hydrocephalus

It is also known as water on the brain, developmental (congenital) or acquired condition in which there is an abnormal accumulation of body fluids within the skull. The congenital form may be associated with other abnormalities. The acquired form may follow meningitis or another cerebral inflammation or tumor. The accumulation of fluid causes compression of the brain and enlargement of the skull, sometimes with separation of bone structures. Paralysis and death may result or, at the least, mental retardation. Many forms of therapy, including surgery, have been attempted, but usually without much success in extreme cases.










hyperinsulinism

The presence in the system of an above-normal amount of insulin, the substance secreted by the pancreas and needed by the body to utilize sugar. An increased amount of insulin in the body results in below-normal amounts of sugar in the system, giving rise to such symptoms as headache, dizziness, weakness, and emotional instability. In severe cases there may be convulsions, coma, and death. The cause of oversecretion of insulin may be organic, i.e., a tumor of the pancreas, impaired liver function, or endocrine disorders, or it may be functional, e.g., unusual muscular exertion, pregnancy, or lactation. In diabetics, hyperinsulinism is known as insulin shock and may occur from overdosage with insulin in the course of treatment. Where there is some organic cause for hyperinsulinism, surgery may be required to eliminate it. Functional hyperinsulinism and insulin shock are treated by dietary measures designed to bring the insulin-sugar ratio into better balance.












hypertrophy

The enlargement of a tissue or organ of the body resulting from an increase in the size of its cells. Such growth accompanies an increase in the functioning of the tissue. In normal physiology the growth in size of muscles (e.g., in an athlete as a result of increased exercise) and also the enlargement of a uterus in pregnancy are caused by hypertrophy of muscle cells. In pathology the thickening of the heart muscle from overstrain, as in hypertension (high blood pressure), is the result of hypertrophy. An organ subjected to extra work (e.g., the one kidney left to function after surgical removal of the other) usually compensates by enlarging; in such cases hyperplasia, an increase in the number of cells, generally accompanies hypertrophy.

I

impetigo

contagious skin infection affecting mainly infants and children. The causative organisms are either hemolytic streptococci or staphylococci. The eruption consists of small red spots or blisters that rupture, discharge, and become encrusted. The infection is easily spread over the skin by fingernails because of its symptomatic itching; it can also be spread by contaminated linen, clothing, or other objects. Effective treatment with antibiotic ointments usually relieves the infection within 10 days. Systemic treatment with antibiotics is sometimes necessary to prevent the nephritis that occasionally develops.









indigestion

indigestion or dyspepsia,discomfort during or after eating caused by some interference with the normal digestive process. Symptoms include nausea, heartburn, abdominal pain, gas distress, and a feeling of abdominal distention. Common indigestion may be a result of poor eating habits, including eating too much or too rapidly, eating during emotional upsets, and swallowing large amounts of air. Excessive smoking may also be a factor. Certain foods and drinks may contribute to indigestion, including such gas-forming vegetables as beans, cabbage, and onions, as well as foods with a high fat content and carbonated or alcoholic beverages. Constipation may also be a cause. Indigestion may be a symptom of such conditions as ulcers and gall bladder inflammation. Persistent indigestion should be diagnosed by a physician.










infarction

The blockage of blood circulation to a localized area or organ of the body resulting in tissue death. Infarctions commonly occur in the spleen, kidney, lungs, brain, and heart. The acute emergency known as myocardial infarction. or heart attack is usually caused by a blockage in one of the coronary arteries that supply blood to the heart muscle. The blockage typically occurs when a blood clot lodges in an area already narrowed by arteriosclerosis; other causes are vasospasms in the arterial walls or viral infection of the heart. Symptoms include a crushing pain in the chest radiated to either arm (more commonly the left arm), the jaw, and the neck. The pain may be experienced, particularly in women, as pain in the shoulder or stomach, instead of the chest, and in some cases there are no symptoms at all. The seriousness of the infarction is dependent upon the amount of heart muscle affected, how long the area is deprived of blood, and whether it affects the natural pacemaker of the heart, setting off arrhythmias such as ventricular fibrillation. Death of heart muscle tissue and heart failure may result; damage to other vital organs, including the brain, may occur if the heart is unable to pump necessary oxygen and blood to them. Confirmation of myocardial infarction is made by electrocardiography and measurement of elevations of white blood cells and certain enzymes. Treatment of acute myocardial infarction may include first aid in the form of cardiopulmonary resuscitation (CPR), an emergency balloon angioplasty, or the administration of beta-blockers and thrombolytic drugs (clot-dissolving drugs), such as tissue plasminogen activator. The healing of an infarction occurs through replacement of the dead tissue by scar tissue.












infection

The invasion of plant or animal tissues by microorganisms, i.e., bacteria, viruses, viroids, fungi, rickettsias, and protozoans. The invasion of body tissues by parasitic worms and other higher organisms is commonly referred to as infestation.

Invading organisms such as bacteria produce toxins that damage host tissues and interfere with normal metabolism; some toxins are actually enzymes that, by breaking down host tissues, prevent the localization of infections. Other bacterial substances destroy the host's phagocytes. Viruses and retroviruses are parasitic on host cells, causing cellular degeneration, as in rabies, poliomyelitis, and AIDS, or cellular proliferation, as in warts and cold sores. Some viruses have been associated with the development of certain cancers. Substances produced by many invading organisms cause allergic sensitivity in the host; the immune response to virus infection has been implicated in some diseases.


Infections may be spread via respiratory droplets, direct contact, contaminated food, or vectors, such as insects. They can also be transmitted sexually and from mother to fetus. Immunity is the term used to describe the capacity of the host to respond to infection. Drugs that help fight infections include antibiotics and antiviral drugs.














infertility

It can be discribed as inability to conceive or carry a child to delivery. The term is usually limited to situations where the couple has had intercourse regularly for one year without using birth control. The term sterility is restricted to lack of sperm production or inability to ovulate. Approximately 40% of reported cases of infertility are due to problems in the male; another 40% to problems in the female; the remaining 20% are of unknown cause or due to problems in both the male and female.


Causes

Infertility can be caused by any interruption in the usual process of fertilization, pregnancy, and birth, which includes ejaculation of normal amounts of healthy sperm, passage of the sperm through the cervix and into the fallopian tube of the female, passage of an ovum (egg) down the fallopian tube from an ovary, fertilization in the fallopian tube, implantation of the fertilized egg in a receptive uterus, and the ability to carry the fetus to term. In women, the most common problems are failure to ovulate and blockage of the fallopian tubes. In men, low sperm count is the most common problem.

Underlying problems include disease, such as diabetes or mumps in adult men, hormonal imbalances, endometriosis, pelvic inflammatory disease (often caused by sexually transmitted diseases, e.g., chlamydia), the abuse of alcohol and other drugs, and exposure to workplace hazards or environmental toxins. Uterine irritation or infection that sometimes accompanies IUD use can also reduce fertility. Occasionally there is a chemical or immunological incompatibility between male and female. Psychological factors are difficult to evaluate because of the stressful nature of infertility itself.

The number of couples seeking treatment for infertility has increased as more of them have postponed childbearing to a later age. In women, fertility begins to decline in the mid-twenties, and continues to decline, more and more sharply, until menopause. Male fertility declines gradually until age forty, then declines more quickly.










inflammation

A reaction of the body to injury or to infectious, allergic, or chemical irritation. The symptoms are redness, swelling, heat, and pain resulting from dilation of the blood vessels in the affected part with loss of plasma and leucocytes (white blood cells) into the tissues. White blood cells communicate with each other via cytokines, which are polypeptides released by cells of the immune system that regulate other cells. They are a broad class of soluble compounds that signal one cell type to another, particularly in response to foreign substances. Granulomas are most common in infectious diseases such as tuberculosis, leishmaniasis, and schistosomiasis, in which the body's defenses, unable to destroy the offending organisms, try to enclose them in a mass of inflammatory cells. Certain types of inflammation result in pus formation, as in an abscess. The leukocytes destroy harmful microorganisms and dead cells, preventing the spread of the irritation and permitting the injured tissue to repair itself.












influenza

influenza or flu,acute, highly contagious disease caused by a virus; formerly known as the grippe. There are three types of the virus, designated A, B, and C, but only types A and B cause more serious contagious infections. Influenza is difficult to diagnose in the absence of an epidemic, since it resembles many common respiratory ailments. It can be distinguished from a cold, however, by sudden fever, prostration, weakness, and sometimes severe muscular aches and pains. Stomach and intestinal symptoms, such as nausea and vomiting, are not commonly due to influenza infection, and the term stomach flu is a misnomer. Influenza is usually self-limiting, but complications such as pneumonia and bronchitis can be serious threats to newborns, the elderly, and people with chronic diseases. The viruses are spread by respiratory droplets, and the disease is typically most widespread from the late fall to early spring.

Vaccination is recommended for persons who are likely to be exposed to influenza (such as health-care workers) or who are at risk for complicatons. The antiviral drugs amantadine and rimantadine are effective against most strains of type A influenza, and zanamivir and oseltamivir against types A and B. Given within two days of the first appearance of symptoms, they may reduce the symptoms; they may also be given to prevent influenza infection in persons exposed to the disease. Uncomplicated influenza requires only rest and treatment of symptoms, and the use of antibiotics has greatly reduced fatalities from secondary infections. Return to normal activity should be undertaken slowly, as relapses are easily precipitated.

Serious influenza in humans is caused by strains of several A subtypes (which are designated by the specific combination of the 19 hemagglutinin and 9 neuraminidase proteins, or antigens, found on the virus's surface, e.g., H1N1) and by strains of type B. Type A is also found in swine, horses, whales, seals, and other animals, but wild birds are the only animals to have all A subtypes, and migratory birds can spread a strain of the disease great distances. Some H5 and H7 strains of avian influenza (also called avian flu or bird flu) are especially virulent and can result in financially devastating losses in the poultry industry. As a result, outbreaks of the disease are usually controlled by severe measures, including killing all poultry within a couple miles of the outbreak. Avian and swine influenza occasionally infect humans, but such cases rarely result in human-to-human transmission.

The influenza vaccine confers immunity only to a particular strain, and immunity to one strain or subtype, whether acquired through infection or vaccination, does not prevent susceptibility to another. Because the surface antigens of flu viruses change over time, it is necessary to reformulate the vaccine yearly in an educated guess at what strain will appear. Abrupt major changes in a virus, which can result in increased virulence, also occur. Swine, which can be infected by avian and human influenzas, can facilitate such a development when avian and human strains are both present in an animal, enabling the genetic material of the two to reassort (mix). A major change can similarly occur in a person who is infected by both human and avian viruses.

Epidemics of influenza may be caused by type A or B strains, although type B is more likely to occur sporadically. Pandemics (worldwide epidemics) are caused only by type A. Three such pandemics occurred in the 20th cent., in 1918–19 (the “Spanish flu”), 1957–58 (the “Asian flu”), and 1968–69 (the “Hong Kong flu”). In 1918–19, some 675,000 people died in the United States, and between 50 and 100 million died worldwide. Research suggests that the 1918–19 strain arose when an avian strain acquired the ability to infect humans, and the other two pandemics are known to have been caused by strains produced by the reassorting of human and avian viruses. The avian strain A (H5N1), first known to have been transmitted directly to humans in 1997, began a new outbreak in several E Asian nations in 2003 and has shown increased virulence when transmitted to humans. International health officials are concerned that it could reassort with a human influenza virus, resulting in a new strain that would be both extremely virulent and highly contagious. By early 2006 the A (H5N1) outbreak had spread across Asia to birds and poultry in many European and some Africa nations. Fewer than 300 cases of A (H5N1) influenza have been identified in humans, largely in Asia; roughly 60% of the cases have been fatal.














insomnia

An abnormal wakefulness or inability to sleep. The condition may result from illness or physical discomfort, or it may be caused by stimulants such as coffee or drugs. However, frequently some psychological factor, such as worry or tension, is the cause. Mild insomnia may often be relieved by a soothing activity like reading or listening to soft music. Chronic or severe insomnia requires treatment of the underlying physical or psychological disorder. In a few, very rare cases, individuals in certain families are subject to an incurable inherited insomia caused by prions that form plaques in the thalamus; the disease appears suddenly in adulthood and ultimately is fatal.

Many patients respond to the assurance that their sleeplessness is a result of normal anxieties or a treatable physical disorder. Opportunities to ventilate anxieties often ease distress and helps resume normal sleeping patterns. Elderly persons are encourage to exercise more during the day; instructed relaxation, administration of tryptophan, and intake of warm milk helps some patients sleep. Sedatives and hypnotics drugs may be employed if the sleeplessness is impairing the subject's sense of well being. Those who wake because of pain receive an analgesic at bedtime; for those who experience insomnia accompanied with depression, an antidepressant often suffices.










iritis

The inflammation of the iris, the pigmented portion of the eye surrounding the pupil. The condition is sometimes associated with diabetes, with rheumatic diseases such as rheumatoid arthritis, and with infections such as syphilis. Iritis may cause severe pain, a swollen, discolored iris, abnormal sensitivity to light, and blurred vision. If not quickly treated, it may result in impaired vision or blindness. Iritis is treated with antibiotics or other drugs to eliminate infection, atropine to dilate the pupil and prevent scarring, and sometimes steroids to reduce inflammation.

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jaundice

An abnormal condition in which the body fluids and tissues, particularly the skin and eyes, take on a yellowish color as a result of an excess of bilirubin. During the normal breakdown of old erythrocytes (red blood cells), their hemoglobin is converted into bilirubin. Normally the bilirubin is removed from the bloodstream by the liver and eliminated from the body in the bile, which passes from the liver into the intestines. There are several conditions that may interrupt the elimination of bilirubin from the blood and cause jaundice. Hemolytic jaundice is caused by excessive disintegration of erythrocytes; it occurs in hemolytic and other types of anemia and in some infectious diseases like malaria. Another type of jaundice results from obstruction in or about the liver; usually a stone or stricture of the bile duct blocks the passage of bile from the liver into the intestines. A third type of jaundice occurs when the liver cells are damaged by diseases such as hepatitis or cirrhosis of the liver; the damaged liver is unable to remove bilirubin from the blood. Treatment of jaundice is directed to the underlying cause. Many instances of obstructive jaundice may require surgery.

K

Kaposi's sarcoma

usually fatal cancer that was considered rare until its appearance in AIDS patients. First described by an Austro-Hungarian physician, Moritz Kaposi, in 1872, it appears in three forms and is characterized by vascular skin tumors. Kaposi's sarcoma is endemic in Africa, where it is more aggressive, seen in children and young men, and accounts for 10% of malignancies in Congo (Kinshasa) and Uganda. A mild form of the disease is sometimes seen in elderly men of Mediterranean origin. The development of AIDS-related Kaposi's sarcoma has been linked to a virus of the herpes group. In the early 1980s it was seen in nearly 50% of AIDS patients, but the proportion has decreased since that time. In AIDS, Kaposi's presents as barely raised pink or red papules or plaques that become widely disseminated on the skin and in the gastrointestinal and respiratory tracts, where they may cause extensive bleeding. Treatment includes chemotherapy or surgical excision, cryosurgury (destruction by freezing), or electrodessication (destruction by heat). Local radiation therapy can also be effective. AIDS patients are treated with Vinblastine, an active, but weak, agent, which further lowers immunity.







kwashiorkor

protein deficiency disorder of children. It is prevalent in overpopulated parts of the world where the diet consists mainly of starchy vegetables, particularly in sections of Africa, Central and South America, and S Asia. Such a diet, although adequate in calories, is deficient in certain amino acids, the constituents of proteins vital for growth. The nursing infant gets the required amino acids from the mother's milk. But the weaned child, who receives neither milk nor meat, is likely to develop kwashiorkor. The most striking manifestations of the disease are a swollen and severely bloated abdomen, resulting from decreased albumin in the blood, and various skin changes resulting in a reddish discoloration of the hair and skin in black African children. Other symptoms include severe diarrhea, enlarged fatty liver, atrophy of muscles and glands, mental apathy, and generally retarded development. Kwashiorkor is treated by adding proteins to the diet, usually in the form of dried milk.

L

laryngitis

inflammation of the mucous membrane of the voice box, or larynx, usually accompanied by hoarseness, sore throat, and coughing. Acute laryngitis is often a secondary bacterial infection triggered by infecting agents causing such illnesses as colds, measles, whooping cough, or influenza. It may also result from straining the voice, drinking hot liquids, or exposure to irritating gases. In chronic laryngitis, inflammation of the mucous membrane of the larynx persists. When such a condition continues for long periods, the membrane becomes irreversibly thickened and the voice permanently changed. Laryngitis resulting from weakened laryngeal muscles is common in singers, teachers, and others who use the voice professionally.











Lassa fever

a severe viral disease occurring mostly in W Africa, characterized by high fever, muscle aches, mouth ulcers, and bleeding in the skin. The disease was first recognized in Lassa, Nigeria, in 1969. The causative virus belongs to a group called arenaviruses and is harbored by a rat, Mastomys natalensis. The virus is spread to humans via the rat's urine in airborne droplets or contaminated food. The disease can also be caught by medical personnel treating patients in hospitals.

The incubation period of Lassa fever is 3 to 17 days. Following fever and general malaise, later stages of the disease may include abdominal pain, diarrhea, vomiting, and petechiae, tiny purplish spots in the skin caused by leakage of blood from the capillaries. Heart and kidney failure may also occur in severe cases, and mortality is high, ranging from about 15% to, among pregnant women, as much as 60%. Treatment by injection of the antiviral drug ribavirin is often successful if begun early.










lead poisoning

An intoxication of the system by organic compounds containing lead. These enter the body by respiration (of dust, fumes, or sprays) or by ingestion of food or other substances that contain lead. Lead poisoning, formerly a leading occupational hazard in industrialized countries, can be an acute episode but is usually a chronic, cumulative disease brought about by continuous exposure.











Legionnaire's disease

An infectious, sometimes fatal, disease characterized by high fever, dry cough, lung congestion, and subsequent pneumonia. Major organs, such as the heart, may be damaged as the disease progresses. The disease struck over 180 people attending an American Legion convention in Philadelphia in July, 1976—hence the name. The causative bacterium, later identified as Legionella pneumophilia, is inhaled via contaminated water droplets, primarily from air conditioning and ventilation systems. A milder form of the disease has also been identified. Treatment is with the antibiotic erythromycin.

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leishmaniasis

any of a group of tropical diseases caused by parasitic protozoans of the genus Leishmania. The parasites live in dogs, foxes, rodents, and humans; they are transmitted by the bites of sand flies. There they infect the very white blood cells that normally would defend the body from such invaders. There are two forms of leishmaniasis. The more serious, called kala-azar or visceral leishmaniasis, affects the internal organs, causing fever, anemia, splenomegaly, and discoloration of the skin. Untreated, it can be fatal. The second, or cutaneous form, leaves deep, disfiguring sores at the site of the bite. Treatment is with amphotericin B and other drugs. Leishmaniasis is rarely seen in the United States, but is prevalent in South Asia, the Middle East, North Africa, and parts of the Mediterranean.













leprosy

leprosy or Hansen's disease is chronic, mildly infectious malady capable of producing, when untreated, various deformities and disfigurements. It is caused by the rod-shaped bacterium Mycobacterium leprae, first described by G. Armauer Hansen, a Norwegian physician, in 1874. The mode of transmission is not fully understood. It is thought to be transmitted by nasal discharges and skin sores, possibly also by contaminated objects and arthropods. Only 5% of those exposed acquire the disease. The onset is intermittent and gradual; symptoms may not appear until years after exposure. It is seldom fatal, but its involvement of the peripheral nerves destroys sensation and makes the patient prone to inadvertent injury.

Types of Leprosy

There are two forms of leprosy. In the tuberculoid form of the disease the skin lesions appear as light red or purplish spots. Tuberculoid leprosy is the more benign type, even though it is accompanied by nerve involvement, which leads to numbness (usually of the extremities), contractures, and ulceration. In lepromatous leprosy the skin lesions appear as yellow or brown infiltrated nodules (protuberances) that affect the mucous membranes of the eyes, nose, and throat. There is a general thickening of the skin, especially the face and ears. Lepromatous leprosy is the more easily spread of the two.














leukemia

The cancerous disorder of the blood-forming tissues (bone marrow, lymphatics, liver, spleen) characterized by excessive production of immature or mature leukocytes and consequently a crowding-out of red blood cells and platelets. It was first named by Rudolf Virchow in 1887.

Incidence and Cause

Leukemia is seen in animals, such as cats, guinea pigs, and cattle, as well as in humans. In humans it can occur at any age, but most types are more prevalent in older people. Possible causes include exposure to certain chemicals (e.g., benzene), chromosomal abnormalities such as Down syndrome, exposure to ionizing radiation, certain drugs (e.g., alkylating agents used in cancer treatment), and infection with retroviruses such as HTLV-I, a relative of the AIDS virus. All of these agents are suspected of causing mutations or other disruptions that interfere with the normal regulation of cell growth and division in leukocytes.


Types

Leukemias are classified as either lymphocytic or myeloid, depending on the type of leukocyte affected. In addition, leukemias are classified as either acute, referring to a rapidly progressing disease that involves immature leukocytes, or chronic, referring to a slower proliferation involving mature white cells. In acute leukemias, immature nonfunctioning leukocytes called blast cells proliferate.

The myeloid leukemias affect white blood cells (myelocytes) that give rise to granulocytes (phagocytic white blood cells that mount an inflammatory immune response). They include chronic myeloid leukemia (CML) and acute myeloid leukemia (AML), also called acute nonlymphocytic leukemia (ANLL). The lymphocytic leukemias affect the white blood cells that give rise to various types of lymphocytes. They include acute lymphocytic leukemia (ALL); chronic lymphocytic leukemia (CLL), also called chronic granulocytic leukemia; and hairy cell leukemia (HCL), a chronic leukemia named for the cells' tiny hairlike projections. The lymphocytic leukemias are sometimes referred to as B cell leukemias or T cell leukemias depending upon whether they arise in antibody-producing B cells (HCL, CLL, and some cases of ALL) or in the T cell lymphocytes involved in cell-mediated immunity (some cases of ALL). (See immunity for a further explanation of the cells of the immune system.) Each of these types may be further classified into subtypes. Most childhood leukemias are of the acute lymphocytic type; acute myeloid leukemia is the most common type of adult leukemia.



Symptoms

Many of the symptoms of acute leukemia can be attributed to anemia, which results from the attrition of red blood cells as they are crowded out by the leukemic cells. Frequent infections result from a dearth of functioning white blood cells. Bone tenderness may also be present. Hemorrhaging may develop because blood-clotting elements are scarce. Blasts may congregate in the lymph nodes, spleen, and liver, causing enlargement and pain, or they may invade the central nervous system, causing dizziness, headache, or fever. If untreated, death can supervene rapidly in acute leukemia.

Patients with chronic leukemias often have no symptoms and may be hard to diagnose, but less virulent versions of the symptoms seen in the acute leukemias may be present. Death from chronic leukemia is usually from infection.













lung cancer

cancerthat originates in the tissues of the lungs. Lung cancer is the leading cause of cancer death in the United States in both men and women. Like other cancers, lung cancer occurs after repeated insults to the genetic material of the cell. By far the most common source of these insults is tobacco smoke, which is responsible for about 85% of U.S. lung cancer deaths (see smoking). The incidence of lung cancer in other countries follows their smoking patterns. Some other carcinogens known to cause lung cancer are found in the workplace. These include bischloromethyl ether and chloromethyl ether in chemical workers, arsenic in copper smelting, and asbestos in shipbuilders and other asbestos workers. Radon poses a risk to uranium and fluorspar miners and may pose a risk in some private residences as well. African Americans have a higher incidence of lung cancer than European Americans, even after adjusting for smoking.


Types of Lung Cancer

Lung cancers are classified according to the type of cell present in the tumor. The majority are referred to as non–small cell carcinomas. These include squamous cell or epidermoid carcinomas (the most common type worldwide), adenocarcinomas, and large cell carcinomas. Small cell carcinoma (which includes the subtypes oat cell and intermediate) comprises approximately 20% to 25% of lung cancers; it often has metastasized by the time it is detected. Lung cancer most commonly spreads to the brain, bone, liver, or bone marrow.

Symptoms

The primary symptoms of lung cancer are cough, shortness of breath, hoarseness, blood in the sputum, and pain. In some types, the cancer cells themselves produce hormones or other substances that can create an imbalance and result in various symptoms. Metastatic lung cancer also can cause symptoms that result from its effect on the organ to which the cancer has spread.











lupus

noninfectious chronic disease in which antibodies in an individual's immune system attack the body's own substances. In lupus, medically known as lupus erythematosus, antibodies are produced against the individual's own cells, causing tissue inflammation and cell damage. Because the vascular and connective tissue of any body organ may be affected, various symptoms may result. Generalized symptoms include fever, weakness, weight loss, anemia, enlargement of the spleen, and a characteristic butterfly-shaped skin rash on the face. Heart, joint, and kidney disease are common (see nephritis). It is believed that the disease may be triggered by certain drugs or foreign proteins, exposure to ultraviolet radiation, or extreme stress. The disease, which may range from mild to fatal, occurs commonly in young women. It is treated with immunosuppressive drugs and steroids.












lymphoma

a cancer of the tissue of the lymphatic system. There are two categories of lymphomas. One type is termed Hodgkin's disease, the other, non-Hodgkin's lymphoma.

lymphoma, non-Hodgkin's

any cancer of the lymphoid tissue (see lymphatic system) in which the Reed-Sternberg cells characteristic of Hodgkin's disease (the other category of lymphoma) are not present. There are about 10 different types of non-Hodgkin's lymphomas, some slower- or faster-growing than others. Non-Hodgkin's lymphoma can affect children as well as adults. In most cases the cause is unknown, but an increased incidence has been observed in people who have been exposed to Agent Orange, and some forms of the disease are frequently seen in people with AIDS, many of these in association with latent Epstein-Barr virus infection.


Symptoms

The first symptom of non-Hodgkin's lymphoma is often a painless swelling of a lymph node in the neck, the groin, or under the arm. Other symptoms include fever, night sweats, itching, and unexplained weight loss. Diagnosis is made by laboratory study of tissue obtained by taking a biopsy of the suspicious lymph node or nodes.

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macular degeneration

eye disorder causing loss of central vision. The affected area, the macula, lies at the back of the retina and is the part that produces the sharpest vision. The most serious visual impairment occurs when abnormal blood vessels form and leak serous fluid or bleed into the tissue of the macula, ultimately producing scar tissue. Peripheral (side) vision is unaffected. Onset may be acute with hemorrhage but usually is gradually progressive. Although some vision is retained, the ability to read, recognize faces, and drive a motor vehicle is greatly reduced. The condition is painless.

Macular degeneration is a major cause of vision impairment among elderly people. Although its underlying cause is unknown, it sometimes appears to run in families. Serious macular degeneraton, if diagnosed early, may have its progress stemmed by laser or photodynamic (cold laser and drug) treatment that closes leaking vessels. Antiangiogenic drugs, which inhibit the formation of new blood vessels, can be injected into the eye to stop degeneration and in some cases even improve vision. Sudden change in vision in someone over age 50 thus requires immediate medical attention.













malaria

An infectious parasitic disease that can be either acute or chronic and is frequently recurrent. Malaria is common in Africa, Central and South America, the Mediterranean countries, Asia, and many of the Pacific islands. In the United States it was found in the South and less frequently in the northern and western parts of the country.

The primary causative organism, Plasmodium falciparum, requires both the Anopheles mosquito and humans to complete its life cycle: sexual reproduction of the protozoan occurs in the mosquito; an immature form is then transmitted to the human via the bite of the mosquito. In a person the parasite goes to the liver, replicates, and moves into the bloodstream, where it attacks red blood cells for their hemoglobin. Some of the plasmodia become sexually mature and are transmitted back to another biting mosquito. Three other Plasmodium species also infect humans.


Symptoms

At the onset of malaria, bouts of chills (ague) and fever lasting several hours and occurring every three or four days are the usual symptoms. If the disease is not treated, the spleen and the liver become enlarged, anemia develops, and jaundice appears. Death may occur from general debility, anemia, or clogging of the vessels of cerebral tissues by affected red blood cells. Cerebral malaria is most commonly seen in infants, pregnant women, and nonimmune travelers to endemic areas.


Immune Response

. falciparum creates protein knobs on the surfaces of the red blood cells it attacks. These knobs attach the cell to the lining of the blood vessel, preventing its removal to the spleen for destruction. The parasite slows detection by the immune system by changing the makeup of the knobs periodically, substituting or rearranging its 150 “var” (variability) genes, a strategy unique to malaria. A pattern of remission and relapse results as the immune system learns each new “code” only to have it again changed. Patients with malaria gradually do develop immunity that modifies the course of the disease, but this immunity has a degree of strain specificity.



Treatment and Control

The bark of the cinchona and its product, quinine, have been used in the treatment of malaria for centuries. After World War II, they were largely replaced by the synthetic analog chloroquine. The use of chloroquine, in addition to the use of DDT for mosquito control, was expected to eradicate the disease, but a World Health Organization campaign (1955–69) to eradicate the disease globally (by controlling mosquitoes long enough to allow the human population to become disease free) proved unsuccessful. Despite that, spraying successfully eradicated the disease in some areas (Sardinia, Japan, and Taiwan).

In the 1960s several strains of the malarial parasite developed resistance to chloroquine. This, plus the growing immunity of mosquitoes to insecticides, has caused malaria to become one the of world's leading re-emerging infectious diseases, infecting an estimated 300 million people a year and killing more than a million. Mefloquine may be used in areas where the disease has become highly resistant to chloroquine, but some strains are now resistant to it and other drugs. Artemisinin (derived from sweet wormwood) in combination with other drugs is now in many cases the preferred treat for resistant strains. Amodiaquine in combination with sulfadoxine and pyrimethamine has also been shown to be effective, and malarone (atovaquone and proguanil) also is used for resistant strains. Vaccines against malaria are still experimental. Spraying is still used to control malaria-transmitting mosquitoes, but fish that feed on mosquito larva also have been employed.











malnutrition

insufficiency of one or more nutritional elements necessary for health and well-being. Primary malnutrition is caused by the lack of essential foodstuffs—usually vitamins, minerals, or proteins—in the diet. In some areas of the world a poor economy or such regional conditions as drought or overpopulation cause a scarcity of certain foodstuffs, and a certain portion of the population is malnourished because essential nutrients are not available. However, even when food is plentiful, malnutrition can result from poor eating habits. Secondary malnutrition is caused by failure of absorption or utilization of nutrients (as in disease of the gastrointestinal tract, thyroid, kidney, liver, or pancreas), by increased nutritional requirements (growth, injuries, burns, surgical procedures, pregnancy, lactation, fever), or by excessive excretion (diarrhea).












measles

highly contagious disease of young children, caused by a filterable virus and spread by droplet spray from the nose, mouth, and throat of individuals in the infective stage. This period begins 2 to 4 days before the appearance of the rash and lasts from 2 to 5 days thereafter. The first symptoms of measles, after an incubation period of 7 to 14 days, are fever, nasal discharge, and redness of the eyes. Characteristic white spots appear in the mouth, followed by a rash on the face that spreads to the rest of the body. The symptoms disappear in 4 to 7 days. One attack of measles confers lifelong immunity. However, it renders the patient susceptible to other more serious infections such as bronchial pneumonia and encephalitis. The measles virus has also been associated with subacute sclerosing panencephalitis (SSPE), which causes chronic brain disease in children and adolescents. After the attack of measles, it can cause intellectual deterioration, convulsive seizures, and motor abnormalities and is usually fatal. Common measles in pregnant women can be a threat to the unborn child, and vaccination of women well before pregnancy is recommended.












meningitis

meningitis or or cerebrospinal meningitis is defined as an acute inflammation of the meninges, the membranes that cover and protect the brain and spinal cord. It can be caused by bacteria, viruses, fungi, or other organisms, usually introduced via the bloodstream from infections elsewhere in the body.

Viral meningitis

sometimes referred to as nonbacterial or aseptic meningitis, is milder and more common than bacterial forms. It can be caused by any of a number of viruses, including enteroviruses, the mumps virus, herpesviruses, HIV, and several mosquito-borne viruses (Bunyavirus and flavivirus) usually associated with encephalitis. Viral meningitis is usually seen only in individual cases rather than in outbreaks. Those not vector-borne are usually spread from person to person by the fecal-oral route. Symptoms include headache, fever, stiff neck, and tiredness, sometimes accompanied by a rash. There is no specific treatment.

Bacterial meningitis

A variety of organisms can cause bacterial meningitis, a serious form that can be fatal, especially in children. Symptoms include high fever, headache, chills, vomiting, stiff neck or back, and confusion, sometimes accompanied by a purplish rash. Serious cases can quickly lead to delirium, coma, or convulsions. It is spread by oral or nasal secretions.

The leading cause of bacterial meningitis is the ill-named bacterium Haemophilus influenzae b (Hib), originally thought to be an influenza virus. It commonly affects infants and children. The second most common bacterial cause of meningitis is Neisseria meningitidis (meningococcus). Meningococcal meningitis affects people of all ages and tends to occur in epidemics, especially among those who live in crowded conditions. An outbreak in the slums of Brazil in 1974–75 killed 11,000 people and left over 75,000 with permanent neurological complications. In 1996, an epidemic centered in the Sahel region of W Africa killed 16,000. In the United States it is seen most often in children and teens.

Strepococcus pneumoniae, also referred to as pneumococcus, is another cause of serious meningitis cases. It is the most common cause of meningitis in adults. It often accompanies pneumococcus infections in other parts of the body, such as the ear or sinuses. Other bacterial causes of meningitis include tuberculosis, leptospirosis, and Lyme disease.

Bacterial meningitis calls for emergency medical care and the administration of antibiotics. Close contacts of patients with bacterial meningitis may receive prophylactic antibiotics, such as rifampin. Definitive diagnosis can be made by laboratory tests of cerebrospinal fluid obtained by a lumbar puncture (spinal tap). Twenty to thirty percent of children who survive bacterial meningitis sustain permanent neurological damage such as deafness, mental retardation, or convulsions. Since the late 1980s, routine vaccination of young children against Hib has virtually eliminated Hib disease in the United States. Routine vaccination against meningococcal meningitis is recommended for pre-adolescents, and vaccination is also recommended for persons in the military or traveling to parts of Africa where the disease is endemic. The meningococcal vaccine does not provide protection against all meningococcus strains.


Fungal meningitis

Fungal meningitis has been on the rise in the United States due to opportunistic infection with Cryptococcus neoformans in people weakened by AIDS. In these patients, it is often fatal. It can be treated with the antifungals amphotericin B and fluconazole. Other causes include coccidioidomycosis and histoplasmosis.













mercury poisoning

tissue damage resulting from exposure to more than trace amounts of the element mercury or its compounds. Elemental mercury (the silver liquid familiar from thermometers) is the most common occupational source. Exposure typically comes from inhaling mercury vapors. Inorganic salts of mercury (e.g., mercurous chloride, or calomel) are used in some products to inhibit the growth of fungi and bacteria. Organic mercury compounds, especially methylmercury, are more toxic than other forms because they easily cross cell membranes. They are most often ingested in contaminated fish.

Mercury poisoning can cause severe neurological and kidney damage. Acute exposure can affect the respiratory and gastrointestinal systems. Organic mercury can cross the blood-brain barrier and cause irreversible nervous system and brain damage, e.g., loss of motor control, numbness in limbs, blindness, and inability to speak. Some studies have connected maternal mercury exposure to fetal damage. Mercury poisoning can be confirmed by urine tests. Chelation therapy is used for poisoning with elemental mercury and mercury salts; there is no treatment for organic mercury poisoning.

Mercury has become an environmental pollutant in areas where eroding mercury-bearing rock or agricultural and industrial wastes containing the metal escape or are discharged into waterways. Mercury also is released into the atmosphere when coal is burned. Elemental mercury and mercury salts, although fairly inert when deposited on the bottom of waterways, are converted into organic mercury, typically methylmercury, by microorganisms. This compound then enters the food chain where it is biomagnified up to 100,000 times in predacious fish. Consumption of toxic fish and of game birds and mammals that feed on fish is the main risk to humans. Minamata disease was named after the occurrence, in the 1950s and 1960s in Minamata, Japan, of many cases of severe mercury poisoning. It was found that a chemicals factory was discharging mercury-containing wastes into the local waters, contaminating fish that residents caught for food.















to be continued

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ஜ иστнιπg ιš ιмթΘรรιвlε тσ α ωιℓℓιиg нєαят ஜ

Interesting!!!

so many diseases... can some one tell me how many are cureable ones in above mention diseases?

migraine

headache characterized by recurrent attacks of severe pain, usually on one side of the head. It may be preceded by flashes or spots before the eyes or a ringing in the ears, and accompanied by double vision, nausea, vomiting, or dizziness. The attacks vary in frequency from daily occurrences to one every few years.

Migraine affects women three times as often as men and is frequently inherited. Many disturbances, such as allergy, temporary swelling of the brain, and endocrine disturbances, have been suspected of causing some varieties of the disorder. Although the exact cause is unknown, evidence suggests a genetically transmitted functional disturbance of cranial circulation. The pain is believed to be associated with constriction followed by dilation of blood vessels leading to and within the brain.

Untreated attacks may last for many hours. Mild attacks are often relieved by common sedatives such as aspirin or codeine. Severe attacks may be treated with any of a variety of drugs, including a group called triptans, by injection or in the form of pills or nasal sprays. Certain beta-blockers, antiepileptic drugs, or tricyclic antidepressants may reduce the recurrence of migraines in some patients. Biofeedback is used in training people to recognize the warning symptoms and to practice control over the vascular dilation that initiates attacks.










infectious mononucleosis

An acute infectious disease of older children and young adults, occurring sporadically or in epidemic form, also known as mono, glandular fever, and kissing disease. The causative organism is a herpesvirus known as Epstein-Barr virus. The disease occurs most often in patients between the ages of 15 and 35. The virus is present in the saliva; it is usually spread by sharing a glass or kissing. Symptoms usually take 30 to 50 days to develop.

Diagnosis of mononucleosis follows the exhibition of a large number of abnormal white blood cells (lymphocytes) on microscopic blood examination. These blood cells have a single nucleus that give the disease its name. Symptoms are varied but include enlarged lymph nodes, sore throat, fever, enlarged spleen in about half the cases, and excessive fatigue. Occasional rashes and throat and mouth infections occur. Liver inflammation is common. Fatalities are very rare and, when they do occur, usually result from splenic rupture. General therapeutic measures include bed rest and treatment of symptoms.













motion sickness

waves of nausea and vomiting experienced by some people, resulting from the sudden changes in movement of a vehicle. The ailment is also known as seasickness, car sickness, train sickness, airsickness, and swing sickness. The principal cause of the disturbance is the effect of motion on the semicircular canals of the inner ear, although other factors such as inadequate ventilation and fumes or noxious odors may contribute. Drugs are available that, when taken beforehand, prevent the occurrence of motion sickness.









multiple chemical sensitivity

multiple chemical sensitivity (MCS) is an adverse physical reaction to certain chemicals in susceptible persons. When exposed to the chemicals, people with MCS react with symptoms such as nausea, headache, dizziness, fatigue, impaired memory, rash, and respiratory difficulty. A wide range of household and industrial chemicals, including cleaning products, tobacco smoke, perfumes, inks, and pesticides, have been implicated as triggers for MCS.

Many researchers do not regard multiple chemical sensitivity as a medically valid syndrome, believing that the depression that frequently accompanies it is an indication that the symptoms are psychological in origin. Others note that descriptions of the syndrome are largely anecdotal and not proven scientifically, or that the imprecisely defined syndrome is easily abused as a diagnosis, pointing to what they feel is an exaggerated number of worker's compensation cases involving MCS. Nevertheless, many sufferers do seem to improve when they eliminate contact with the chemicals known to trigger their condition; in extreme cases this may mean confinement to specially treated living quarters.










multiple sclerosis

multiple sclerosis (MS), chronic, slowly progressive autoimmune disease in which the body's immune system attacks the protective myelin sheaths that surround the nerve cells of the brain and spinal cord (a process called demyelination), resulting in damaged areas that are unable to transmit nerve impulses. The disease also gradually damages the nerves themselves. There are elevated numbers of lymphocytes in the cerebral spinal fluid and of T cells in the blood.

The onset of MS is usually at age 20 to 40 years, and its many symptoms affect almost every system of the body. There may be visual difficulties, emotional disturbances, speech disorders, convulsions, paralysis or numbness of various regions of the body, bladder disturbances, and muscular weakness. The course of the disease varies greatly from person to person. In some patients, the symptoms remit and return, sometimes at frequent intervals and sometimes after several years. In others the disease progresses steadily.

There is a genetic predisposition to MS, and environmental factors also seem to play some role. The disease is more common in temperate climates (1:2,000) than in the tropics (1:10,000).

There is no cure for MS, but a number of drugs—the first of which became available in the 1990s—can slow its underlying progress and reduce the frequency of attacks. These are Avonex, Rebif, and Betaseron, forms of beta interferon (a synthetic version of a natural substance produced by the immune system); Copaxone (glatiramer acetate); and Tysabri (natalizumab).









mumps

mumps (epidemic parotitis) is an acute contagious viral disease, manifesting itself chiefly in pain and swelling of the salivary glands, especially those at the angle of the jaw. Other symptoms are fever, a general feeling of illness, and pain on chewing or swallowing. Mumps most often affects children between the ages of 5 and 15, the incubation period being 14 to 21 days; the acute phase rarely lasts more than 3 days. The disease is usually more severe in adults, the most common complications being pain and swelling of the testes (in 20% of adult male patients) and swelling of the meninges that cover the brain and spinal cord (in about 30% of cases). Sterility resulting from involvement of the testes and fatalities from the meningoencephalitis occur in a small minority of male cases. Other possible complications include pancreatitis and involvement of the heart or thyroid. The ovaries are sometimes affected in females. Treatment consists mainly of bed rest, intake of fluids, and the administration of analgesics. A live virus vaccine has been developed that can be given to susceptible children at 15 months.











muscular dystrophy

any of several inherited diseases characterized by progressive wasting of the skeletal muscles. There are five main forms of the disease. They are classified according to the age at onset of symptoms, the pattern of inheritance, and the part of the body primarily affected.


Types of Muscular Dystrophy

The most common form of muscular dystrophy, Duchenne, was first described by the French physician Guillaume Benjamin Amand Duchenne in 1861. Most cases are caused by a recessive sex-linked gene located on the X chromosome and carried only by females. Each son of a carrier has a 50% chance of inheriting the gene and developing the disease. Each daughter has a 50% chance of inheriting the gene and becoming a carrier. In small number of “sporadic” cases there is no family history. The disease begins with leg weakness before age 3 and progresses rapidly, with death often occurring before age 30, often because of involvement of lung or heart muscle. Research has shown that the abnormal gene fails to produce an essential skeletal muscle protein called dystrophin. Becker's muscular dystrophy is similar to the Duchenne form, but appears somewhat later in life and progresses more slowly.

Fascioscapulohumeral muscular dystrophy primarily involves facial and shoulder muscles and affects both sexes. Symptoms can begin from adolescence to around age 40. It is caused by an autosomal dominant trait (at least one parent will have the disease). Progression is usually slow and severe disability is unusual.

Myotonic muscular dystrophy is another autosomally dominant disease affecting both sexes. It appears to be caused by the repetition of a section of DNA on chromosome 4. In a surprising development, researchers found that the number of repetitions on the chromosome increase and the disease becomes more severe with each generation. It is characterized by an inability of the muscles to relax properly after contraction and primarily affects the muscles of the hands and feet. It usually begins in adulthood and is often accompanied by cataracts, baldness, and abnormal endocrine function.

The limb-girdle form of the disease first affects the muscles of the hip and shoulder areas. Symptoms usually become apparent in late adolescence or early adulthood. Caused by an autosomal recessive trait (carried by a gene passed on by both asymptomatic parents), it can affect males and females alike. This form usually progresses slowly.


Treatment

There is no known treatment or cure for muscular dystrophy. Supportive measures and exercises can improve the quality of life and preserve mobility for as long as possible. Scientists have begun to identify the genetic abnormalities responsible for multiple dystrophy and hope that further understanding will lead to treatment. Genetic screening is recommended for all family members who might be carriers. Prenatal tests such as chorionic villus sampling and amniocentesis can detect some forms of muscular dystrophy early in a pregnancy.









myasthenia gravis

A chronic disorder of the muscles characterized by weakness and a tendency to tire easily. It is caused by an autoimmune attack on the acetylcholine receptor of the post synaptic neuromuscular junction. The initiating event leading to antibody production is unknown. The disease is most common between the ages of 20 and 40 and more frequent in women. The muscles of the neck, throat, lips, tongue, face, and eyes are primarily involved. Exertion quickly brings on difficulty in swallowing, chewing, and talking. The eyelids may droop, and there are visual disorders. Myasthenia gravis is transmitted passively to fetuses from infected mothers, a syndrome call neonatal myasthenia. Congenital myasthenia is a rare autosomal recessive disorder of neuromuscular transmission beginning in childhood, usually with ophthalmoplegia. Life-threatening myasthenic crisis, in which the diaphragm is affected and the patient has respiratory failure, occurs in 10% of the patients. Treatment of the disease includes the use of cholinesterase inhibitors, thymectomy, corticosteroids, and immunosuppressive agents and plasmapheresis (see apheresis). Prolonged rest is likely to restore some of the muscle function; restricted activity at all times and complete rest during periods of aggravation of the illness are necessary.












myxedema

Condition associated with severe hypothyroidism and lack of thyroid hormone in the adult. In the child it is known as cretinism. Symptoms include a dry swelling of the skin, slowed speech and mental awareness, deepened voice, intolerance to cold, fatigue and weakness, and nonspecific degeneration of the heart. Most cases result from atrophy of the thyroid from unknown causes, although surgical removal or irradiation of the gland also precipitates the disorder. Myxedema is treated by administering synthetic preparations of thyroxine (thryoid hormone), liothyronine (triiiodothyronine), a combination of the two synthetic hormones, and desicated animal thyroid.









@ Mahin

Thanx for appreciation. Well, Every disease can be proved harmful. By reading all of them, you will know about all scenario.

Take care,

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N

narcolepsy

a sleep disorder characterized by excessive daytime sleepiness and recurring unwanted episodes of sleep (“sleep attacks”). People with narcolepsy may abruptly fall asleep at almost any time, including while talking, eating, or even walking. The attacks may range from embarrassing or inconvenient to severely disabling, interfering with a person's daily life. An estimated 125,000–250,000 people in the United States have narcolepsy; it occurs about equally in males and females.

Most people with narcolepsy also experience cataplexy, sudden muscular weakness without loss of consciousness, which usually accompanies laughter or anger. Other symptoms, occurring just after falling asleep or upon awakening, include sleep paralysis (a feeling that one cannot move) and vivid hallucinations.

The cause of narcolepsy is not known with certainty, and there is no cure. Treatment, including regular planned naps and the use of stimulant drugs (e.g., amphetamines) plus antidepressants for cataplexy, can help to control its symptoms.









nausea

sensation of discomfort, or queasiness, in the stomach. It may be caused by irritation of the stomach by food or drugs, unpleasant odors, overeating, fright, or psychological stress. It is usually relieved by vomiting. Nausea is frequently present during the early months of pregnancy, and it is a concomitant of motion sickness. However, nausea may also be the symptom of a serious illness; thus persistent nausea should receive medical attention.











nearsightedness

nearsightedness or myopia is the defect of vision in which far objects appear blurred but near objects are seen clearly. Because the eyeball is too long or the refractive power of the eye's lens is too strong, the image is focused in front of the retina rather than upon it. Corrective eyeglasses with concave lenses compensate for the refractive error and help to focus the image on the retina. Hard corneal contact lenses or soft hydrophilic contact lenses are another option, usually offering better acuity and peripheral vision than do eyeglasses. (Contact lenses may be troublesome for people who tend to get eye infections or have hand tremors, however.) Nearsightedness can also be corrected by using laser cornea surgery and a device called a microkeratome to flatten the eye, or by surgically implanting a corrective lens behind the iris.











neoplasm

neoplasm or tumor is a tissue composed of cells that grow in an abnormal way. Normal tissue is growth-limited, i.e., cell reproduction is equal to cell death. Feedback controls limit cell division after a certain number of cells have developed, allowing for tissue repair but not expansion. Tumor cells are less responsive to these restraints and can proliferate to the point where they disrupt tissue architecture, distort the flow of nutrients, and otherwise do damage.

Tumors may be benign or malignant. Benign tumors remain localized as a discrete mass. They may differ appreciably from normal tissue in structure and excessive growth of cells, but are rarely fatal. However, even benign tumors may grow large enough to interfere with normal function. Some benign uterine tumors, which can weigh as much as 50 lb (22.7 kg), displace adjacent organs, causing digestive and reproductive disorders. Benign tumors are usually treated by complete surgical removal. Cells of malignant tumors, i.e., cancers, have characteristics that differ from normal cells in other ways beside cell proliferation. For example, they may be deficient in some specialized functions of the tissues where they originate. Malignant cells are invasive, i.e., they infiltrate surrounding normal tissue; later, malignant cells metastasize, i.e., spread via blood and the lymph system to other sites.

Both benign and malignant tumors are classified according to the type of tissue in which they are found. For example, fibromas are neoplasms of fibrous connective tissue, and melanomas are abnormal growths of pigment (melanin) cells. Malignant tumors originating from epithelial tissue, e.g., in skin, bronchi, and stomach, are termed carcinomas. Malignancies of epithelial glandular tissue such as are found in the breast, prostate, and colon, are known as adenocarcinomas. Malignant growths of connective tissue, e.g., muscle, cartilage, lymph tissue, and bone, are called sarcomas. Lymphomas and leukemias are malignancies arising among the white blood cells. A system has been devised to classify malignant tissue according to the degree of malignancy, from grade 1, barely malignant, to grade 4, highly malignant. In practice it is not always possible to determine the degree of malignancy, and it may be difficult even to determine whether particular tumor tissue is benign or malignant.












nephritis

The inflammation of the kidney. The earliest finding is within the renal capillaries (glomeruli); interstitial edema is typically followed by interstitial infiltration of lymphocytes, plasma cells, eosinophils, and a small number of polymorphonuclear leukocytes. The disease is thought to be immunological, but immunoglobulins and drug antigens have been found in only a few cases. The damage is usually reversible when the cause is recognized and removed, but severe cases can progress to fibrosis and renal failure. The disease can take several forms. Pyelonephritis is usually associated with a bacterial infection transmitted from the bladder or blood; it affects the renal pelvis and is treated with antibiotics. Glomerulonephritis, or Bright's disease, causes degenerative changes in the glomeruli and is believed to be an allergic response to infection elsewhere in the body. Symptoms include headache, mild fever, puffiness of the eyes and face, high blood pressure, and discoloration of the urine. Treatment includes bed rest and limiting the intake of water, sodium, and proteins, and, if necessary, dialysis; antibiotics are given to halt infections (e.g., streptococcal) invasion. The disease occurs more frequently among the young. About 95% of patients recover from the acute phase of the disease; however, if glomerulonephritis becomes chronic, renal damage results after many years, causing kidney failure..













nephrosis

kidney disease characterized by lesions of the epithelial lining of the renal tubules, resulting in marked disturbance in the filtration function and the consequent appearance of large amounts of protein (albumin) in the urine (see urinary system). The nephrotic syndrome can result from a number of conditions including streptococcal infection in children leading to chronic glomerulonephritis, reaction to toxins, diabetes, collagen disease, and other end-stage kidney diseases. The major symptom is massive edema. Corticosteroid therapy has been successful in treating certain forms of the disease.











neuralgia

An acute paroxysmal pain along a peripheral sensory nerve. Unlike neuritis, there is no inflammation or degeneration of nerve tissue. Neuralgia occurs commonly in the area of the facial, or trigeminal, nerve and brings attacks of excruciating pain at varying intervals. Often no cause can be found for trigeminal neuralgia, and in severe cases deadening of the nerve with novocaine or alcohol, or even surgical interruption of the nerve, is necessary to bring relief. Neuralgia can be caused by such disturbances as diabetes, infections, diseases of the nervous system, anemia, and extreme cold. The pain may occur for many months after an attack of shingles (see herpes zoster), and it is one of the symptoms of syphilitic involvement of the central nervous system. In many cases, pain can be relieved by hot applications, drugs, and various kinds of physiotherapy.











neuritis

The inflammation of a peripheral nerve, often accompanied by degenerative changes in nervous tissue. The cause can be mechanical (injury, pressure), vascular (occlusion of a vessel or hemorrhage into nerve tissue), infectious (invasion by microorganisms), toxic (metallic or chemical poisoning, alcoholism), or metabolic (vitamin deficiencies, pernicious anemia). Symptoms of neuritis that arise from involvement of sensory nerves are tingling, burning, pin-and-needle sensations, or even loss of sensation. If motor nerves are involved, symptoms may range from a slight loss of muscle tone to paralysis. Since neuritis is regarded as a condition that results from a number of disorders, rather than a disease in itself, treatment is directed first at the underlying cause.








night blindness

An inability to see normally in subdued light. It is usually a result of vitamin A deficiency. The rod cells, one of two light-sensitive areas of the retina of the eye, are impaired in their capacity to produce a chemical compound called rhodopsin, or visual purple, that is necessary for the perception of objects in dim light. Consequently, the visual threshold, or the minimum intensity of light necessary for sight, is greatly increased. Folk medicine has long recognized the role of the ingestion of liver in alleviating the condition, but it was not until the first quarter of the 20th cent. that vitamin A was identified as the crucial element. Treatment of night blindness consists of the oral or intravenous administration of vitamin A.












nosebleed

nasal hemorrhage occurring as the result of local injury or disturbance. Most nosebleeds are not serious and occur when one of the small veins of the septum (the partition between the nostrils) ruptures. These will usually stop without treatment or when pressure is applied to the nose. A nosebleed may also occur in association with infections, heart failure, hypertension (high blood pressure), arteriosclerosis, scurvy, leukemia, hemophilia, and other disorders. Persistent nosebleeds should be brought to the attention of a physician, who can stop the bleeding with vasoconstrictors and topical anesthetics.

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O

obesity

A condition resulting from excessive storage of fat in the body. Obesity has been defined as a weight more than 20% above what is considered normal according to standard age, height, and weight tables, or by a complex formula known as the body mass index. It has been estimated that 30% to 35% of Americans are overweight or obese.


Health and Social Implications

Obesity is a major public health concern because it predisposes the individual to many disorders, such as noninsulin-dependent diabetes, hypertension, stroke, and coronary artery disease, and has been associated with an increased incidence of certain cancers, notably cancers of the colon, rectum, prostate, breast, uterus, and cervix. In contemporary American society, obesity also carries with it a sometimes devastating social stigma. Obese people are often ostracized, and discrimination against them, especially in hiring and promotion, is common.


Causes of Obesity

Obesity research has yielded a complicated picture of the underlying causes of the condition. The simple cause is ingestion of more calories than are required for energy, the excess being stored in the body as fat. Inactivity and insufficient exercise can be contributing factors; the less active the person, the fewer calories are needed to maintain normal body weight. Overeating may result from unhealthful patterns of eating established by the family and cultural environment, perhaps exacerbated by psychological distress, an emotional dependence on food, or the omnipresence of high-calorie foods.

In some cases, obesity can come from an eating disorder. It has been shown, for example, that binging for some people releases natural opiates in the brain, providing a sense of well-being and physical pleasure. Other studies have found a strong relationship between obesity in women and childhood sexual abuse.

Some weight-loss experts see obesity as based upon genetics and physiology rather than as a behavioral or psychological problem. For example, rat studies have shown that fat cells secrete a hormone that helps the rat's brain assess the amount of body fat present. The brain tries to keep the amount of that hormone (which also appears to act on the brain area that regulates appetite and metabolic rate) at a set level, resulting in the so-called set point—a weight that the body comes back to, even after resolute dieting. The gene that encodes this hormone, called the obese or ob gene, has been isolated in both rats and humans. In addition, a gene that influences obesity and the onset of diabetes has been identified. It has been estimated that from 8 to 30 different genes may influence obesity.



Treatment

Radical treatments for weight loss have included wiring shut the jaw, stapling the stomach, and intestinal bypass operations circumventing a large area of the small intestine, limiting the area where food is absorbed. The “diet pills” of the 1960s, essentially amphetamines such as Dexedrine, are now seldom prescribed for weight loss. Fenfluramine and dexfenfluramine, drugs formerly used to achieve short-term weight loss, were withdrawn from the market following concerns that they could cause heart valve damage. Drugs available by the late 1990s included sibutramine (Meridia), which is an appetite suppressant, and orlistat (Xenical), which acts to block absorption of dietary fat in the intestine. In 2007 an over-the-counter version of orlistat was approved by the Food and Drug Administration.

Although the study of obesity is yielding many possibilities for treatment, the main focus remains diet (especially a diet limiting fat calories) and exercise, often coupled with emotional and behavioral support. The long-term weight-loss success of most attempts at dieting, however, is notoriously low. Groups such as Overeaters Anonymous, modeled after Alcoholics Anonymous, give support to people with weight problems and eating disorders.
















occupational disease

An illness incurred because of the conditions or environment of employment. Unlike with accidents, some time usually elapses between exposure to the cause and development of symptoms. In some instances, symptoms may not become evident for 20 years or more.


Sources of Occupational Disease

Among the environmental causes of occupational disease are subjection to extremes of temperature (leading to heatstroke or frostbite), unusual dampness (causing diseases of the respiratory tract, skin, or muscles and joints) or changes in atmospheric pressure (causing decompression sickness, or the bends), excessive noise (see noise pollution), and exposure to infrared or ultraviolet radiation or to radioactive substances. The widespread use of X rays, radium, and materials essential to the production of nuclear power has led to an especial awareness of the dangers of radiation sickness; careful checking of equipment and the proper protection of all personnel are now mandatory.

In addition there are hundreds of industries in which metal dusts, chemical substances, and unusual exposure to infective substances constitute occupational hazards. The most common of the dust- and fiber-inspired disorders are the lung diseases caused by silica, beryllium, bauxite, and iron ore to which miners, granite workers, and many others are exposed and those caused by asbestos.

Fumes, smoke, and toxic liquids from a great number of chemicals are other occupational dangers. Carbon monoxide, carbon tetrachloride, chlorine, creosote, cyanides, dinitrobenzene, mercury, lead, phosphorus, and nitrous chloride are but a few of the substances that on entering through the skin, respiratory tract, or digestive tract cause serious and often fatal illness.

Occupational hazards also are presented by infective sources. Persons who come into contact with infected animals in a living or deceased state are in danger of acquiring such diseases as anthrax and tularemia. Doctors, nurses, and other hospital personnel are prime targets for the tuberculosis bacillus and for many other infectious organisms.


Worker Protection

Recognition of the effects of working under deleterious conditions and with harmful substances has resulted in efforts to protect workers from exposure to them. Legislation to prevent or limit the occurrence of occupational disease dates from the Factory Act in England in 1802. Prevention of unhealthy or unsafe working conditions and oversight of healthy and safe workplaces are the responsibility in the United States of the federal Occupational Safety and Health Administration (OSHA) and Environmental Protection Agency, as well as many state agencies. Many occupational abuses have been redressed by litigation and legislation in the United States, and workers' compensation takes care, by a system of insurance, of those who suffer from occupational diseases.

















osteomyelitis

An infection of the bone and bone marrow. Direct infection of bone usually occurs through open fractures, penetrating wounds, or surgical operations. Infecting microorganisms may also reach the bone via the bloodstream, the most common means of bone infection in children. Osteomyelitis is characterized by pain, high fever, and formation of an abscess at the site of infection. Infection may be caused by a variety of microorganisms, including staphylococci, streptococci, and other pathogenic bacteria. Unless treated vigorously with antibiotics and sometimes surgery, bone destruction may result.












osteoporosis

A disorder in which the normal replenishment of old bone tissue is severely disrupted, resulting in weakened bones and increased risk of fracture; osteopenia results when bone-mass loss is significant but not as severe as in osteoporosis. Although osteoporosis can occur in anyone, it is most common in thin white women after menopause.

Bone mass is typically at its greatest during a person's mid-twenties; after that point there is a gradual reduction in bone mass as bone is not replenished as quickly as it is resorbed. In postmenopausal women the production of estrogen, a hormone that helps maintain the levels of calcium and other minerals necessary for normal bone regeneration, drops off dramatically, resulting in an accelerated loss of bone mass of up to 3% per year over a period of five to seven years. Smoking, excessive alcohol consumption, and a sedentary lifestyle increase the risk of bone-mass loss; a diet high in protein and sodium also speed calcium loss. The disorder also has a genetic component. A vitamin D receptor gene that affects calcium uptake and bone density has been identified, and the different forms of this gene appear to correlate with differences in levels of bone density among osteoporosis patients.

Osteoporosis has no early symptoms and is usually not diagnosed until a fracture occurs, typically in the hip, spine, or wrist. A diagnostic bone density test is thus recommended as a preventive measure for women at high risk. Treatment can slow the process or prevent further bone loss. Estrogen replacement therapy for postmenopausal women is effective but has potential side effects. Calcitonin, a thyroid hormone, is administered in some cases. Nonhormonal drugs for the treatment of osteoporosis include alendronate (Fosamax) and risedronate (Actonel), bisphosphonates that decrease bone resorption, and raloxifene (Evista), a selective estrogen receptor modulator that can increase bone mineral density. Teriparatide (Forteo), which consists of the biologically active region of human parathyroid hormone, stimulates the activity of osteoblasts, the specialized cells that form new bone. Dietary and supplemental calcium and vitamin D are usually recommended for people at risk, but a seven-year study of more than 36,000 women over 50 that was released in 2006 found that supplements conferred little benefit. Exercise, including weight training, has been found to strengthen bones directly and to improve muscle strength and balance and thus minimize the chance of falls.

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P

pain

An unpleasant or hurtful sensation resulting from stimulation of nerve endings. The stimulus is carried by nerve fibers to the spinal cord and then to the brain, where the nerve impulse is interpreted as pain. The excessive stimulation of nerve endings during pain is attributed to tissue damage, and in this sense pain has protective value, serving as a danger signal of disease and often facilitating diagnosis. Unlike other sensory experiences, e.g., response to touch or cold, pain may be modified by sedatives and nonsteroidal anti-inflammatory drugs or, if unusually severe, by opioid narcotics. Recently, patient-controlled analgesic techniques have been introduced, in which patients have the option of injecting small quantities of narcotic type analgesics to control their own pain. Microprocessor-controlled injections may be made through intravenous catheters, or through a catheter into the epidural (covering of the spinal cord) area. If such treatments do not suffice and if the cause of the pain cannot be removed or treated, severing a nerve in the pain pathway may bring relief.

Pain is occasionally felt not only at the site of stimulation but in other parts of the body supplied by nerves in the same sensory path; for example, the pain of angina pectoris or coronary thrombosis may extend to the left arm. This phenomenon is known as referred pain. Subjective or hysterical pain originates in the sensory centers of the brain without stimulation of the nerves at the site of the pain.

Progress has been made in the management of chronic pain and in the education of patients and physicians in such techniques as biofeedback, acupuncture, and meditation and the appropriate use of narcotics and other medications. Using advanced medical-imaging technology, researchers have now located multiple pain centers in the cerebral cortex of the brain, offering promise of possible improvements in measuring and managing pain.









palpitation

An abnormal heartbeat that is often associated with a sensation of fluttering or thumping. The normal heartbeat is not noticeable to the individual. Palpitation may be a symptom of organic heart disease or of other body disorders such as an overactive thyroid gland or anemia. In healthy persons palpitation can be brought on by undue exertion, shock, excitement, or stimulants.









paraplegia

It means paralysis of the lower part of the body, commonly affecting both legs and often internal organs below the waist. When both legs and arms are affected, the condition is called quadriplegia. Paraplegia and quadriplegia are caused by an injury or disease that damages the spinal cord, and consequently always affects both sides of the body. The extent of the paralysis depends on the level of the spinal cord at which the damage occurs. For example, damage to the lowest area of the cord may result only in paralysis of the legs, whereas damage farther up on the cord causes possible loss of control over the muscles of the bladder and rectum as well or, if occurring even higher, may result in paralysis of all four limbs and loss of control over the muscles involved in breathing.

Most frequently the cause is an injury that either completely severs the spinal cord or damages some of the nervous tissue in the cord. Such damage could result from broken vertebrae that press against the cord. Diseases that cause paraplegia or quadriplegia include spinal tuberculosis, syphilis, spinal tumors, multiple sclerosis, and poliomyelitis. Sometimes when the disease is treated and cured, the paralysis disappears, but usually the nerve damage is irreparable and paralysis is permanent. Treatment of paraplegia and quadriplegia is aimed at helping to compensate for the paralysis by means of mechanical devices and through psychological and physical therapy.











paralysis

paralysis or palsy may be viewed as complete loss or impairment of the ability to use voluntary muscles, usually as the result of a disorder of the nervous system. The nervous tissue that is injured may be in the brain, the spinal cord, or in the muscles themselves. Accordingly there may be general paralysis, involvement of only one side (hemiplegia), paralysis on both sides at one level (paraplegia or quadriplegia), or localized paralysis in a small group of nerves or muscles.

The cause of paralysis may be any injury that tears or compresses the nerves; it may be hemorrhage, tumor, infection, or substances toxic to nerve tissue. One of the most frequent causes of paralysis is stroke, in which hemorrhage, thrombosis, or obstruction of a cerebral vessel interferes with nerve function. Another disorder in which a resting tremor is one of the main symptoms, accompanied by slowness and poverty of movement, muscular rigidity, and postural instability is Parkinson's disease. Cerebral palsy is due to an injury to the brain motor tissue before or during birth. However, this disorder is nonprogressive. Partial or complete paralysis often accompanies multiple sclerosis.












parvovirus

any of several small DNA viruses that cause several diseases in animals, including humans. In humans, parvoviruses cause fifth disease, or erythema infectiosum, an acute disease usually affecting young children. Symptoms include a rash that spreads from the cheeks (hence the common name slap-cheek disease) to the extremities, low fever, fatigue, and, in adults, mild to severe joint pain and swelling. Treatment consists of bed rest, fluids, and acetaminophen for the fever. Parvoviruses have also been associated with aplastic anemia, arthritis, and spontaneous abortion in humans.

Dogs, wolves, and coyotes can become infected with canine parvovirus. Puppies are most susceptible to the virus, which causes diarrhea, vomiting, and fever. There was an outbreak of canine parvovirus in the United States in 1978, and it has become more common worldwide since then. Feline distemper, also called feline panleukopenia, an often fatal disease of cats, raccoons, and minks caused by a parvovirus, is characterized by fever, dehydration, loss of appetite, and a reduction in white blood cells. Annual vaccination against parvoviruses is routine in cats and dogs.












Parkinson's disease

Parkinson's disease or Parkinsonism,degenerative brain disorder first described by the English surgeon James Parkinson in 1817. When there is no known cause, the disease usually appears after age 40 and is referred to as Parkinson's disease. Parkinsonism usually refers to similar symptoms resulting from head injury, encephalitis, syphilis, carbon monoxide poisoning, cerebral arteriosclerosis, or use of MPTP (a synthetic narcotic). The disorder is also termed paralysis agitans, or shaking palsy.

Parkinson's disease is a debilitating and progressive disorder in which the chemicals that facilitate electrical transmission between nerve cells are depleted. It was the first disease to be treated by drugs that replace deficient neurotransmitters. Symptoms usually begin in middle to later life with trembling of the lips and hands, loss of facial expression, and muscular rigidity. As it progresses it may bring on body tremors, particularly in muscles at rest. Movements become slow and difficult; walking degrades to a shuffle. After many years physical incapacity may occur. Dementia occurs in at least 50% of the patients; depression is also common.

When drugs such as levodopa (L-Dopa) are taken orally, many of the worst symptoms are lessened. New drugs such as pramipexole (Mirapex) and ropinirole (Requip) can delay the need for levodopa. Apomorphine (Apokyn) is used treat episodes of reduced mobility in patients with advanced Parkinson's that responds less effectively to levodopa. Future approaches to treatment include a focus on early detection and slowing progression of the disease. Encouraging results have been reported from surgical insertion of a pacemakerlike device deep in the brain to suppress uncontrolled movements, but surgical transplantation of fetal dopamine-producing cells failed to show significant benefits in a controlled study. Traditional surgery can alleviate some tremors, and physical therapy may help mobility.











pellagra

pellagra is deficiency disease due to a lack of niacin (nicotinic acid), one of the components of the B complex vitamins in the diet. Niacin is plentiful in yeast, organ meats, peanuts, and wheat germ. The disease manifests itself in lesions of the skin and mucous membrane, diarrhea and other gastrointestinal symptoms, neurological derangement, and mental confusion. It is most common in areas where the diet consists mainly of corn, which, unlike other grains, lacks niacin as well as the amino acid tryptophan, which the body uses to synthesize the vitamin. Treatment includes large doses of niacin and the institution of a proper diet to prevent recurrences.









pelvic inflammatory disease

pelvic inflammatory disease (PID), infection of the female reproductive organs, usually resulting from infection with the bacteria that cause chlamydia or gonorrhea. The infection typically first affects the cervical area, then spreads to the uterus, fallopian tubes, ovaries, and abdomen. Symptoms may be absent but usually include pelvic pain and vaginal discharge. PID can cause abscesses and scarring in the fallopian tubes that can block fertilization or interrupt the egg's progress, resulting in ectopic (tubal) pregnancy and loss of the fetus. Over 1 million women are diagnosed with PID each year in the United States; 100,000 typically become infertile.












peritonitis

An acute or chronic inflammation of the peritoneum, the membrane that lines the abdominal cavity and surrounds the internal organs. It is caused by invasion of bacterial agents or irritant foreign matter during rupture of an internal organ, by spreading infection from the female genital tract, by penetrating injuries of the abdominal wall, by dissemination of infections through the blood and lymphatic channels, or by accidental pollution during surgery. Typically, peritonitis is a serious complication of another abdominal disorder, such as appendicitis, ulcers, colitis, or rupture of the gall bladder. Severe abdominal pain, vomiting, prostration, and high fever are predominant symptoms. Treatment includes antibiotic therapy and the identification and elimination of the cause of the infection.











phenylketonuria

An inherited metabolic disorder caused by the absence of a specific enzyme (phenylalanine hydroxylase). The absence of this enzyme, a recessive trait, prevents the body from making use of phenylalanine, one of the amino acids in most protein-rich foods, and almost always leads to mental retardation and schizoid changes; convulsions also commonly occur. Early diagnosis and treatment, which includes a carefully regulated low-phenylalanine diet begun during the first few weeks of life, may prevent serious mental deficiency. Positive improvement has been seen even when therapy is started in well-established cases. Most states have made the PKU blood or urine test mandatory for all newborn infants.












phlebitis

An inflammation of a vein. Phlebitis is almost always accompanied by a blood clot, or thrombus, in the affected vein, a condition known as thrombophlebitis. Blood-clot formation may follow injury or be associated with infections. Thrombophlebitis of deep veins, usually in the legs or pelvis, may occur in patients recovering from childbirth, surgery, or other conditions requiring prolonged bedrest; the clotting mechanism is thought to be impaired when the legs are immobilized. Pregnancy or the use of oral contraceptives predisposes some women to thrombophlebitis. The major danger is that a clot originating in the leg vein may dislodge and travel to the lung, a condition known as pulmonary embolism. To avoid the risk of embolism, thrombophlebitis is usually treated with anticoagulants.











pimple

small pointed elevation of the skin that may or may not contain pus. The formation of pimples is frequently associated with infection, irritation, or overactivity of the sebaceous and sweat glands. Repeated eruptions of pimples are often termed acne.










plague

any contagious, malignant, epidemic disease, in particular the bubonic plague and the black plague (or Black Death), both forms of the same infection. These acute febrile diseases are caused by Yersinia pestis (Pasteurella pestis), discovered independently by Shibasaburo Kitasato and Alexandre Yersin in 1894, a bacterium that is transmitted to people by fleas from rats, in which epidemic waves of infection always precede great epidemics in human populations. Sylvatic plague, still another form, is carried by other rodents, e.g., squirrels, rabbits, chipmunks, in rural or wooded areas where they are prevalent.

Bubonic plague, the most common form, is characterized by very high fever, chills, prostration, delirium, hemorrhaging of the small capillaries under the skin, and enlarged, painful lymph nodes (buboes), which suppurate and may discharge. Invasion of the lungs by the organism (pneumonic plague) may occur as a complication of the bubonic form or as a primary infection. Pneumonic plague is rapidly fatal and is the only type that can be spread from person to person (by droplet spray) without intermediary transmission by flea. In the black form of plague, hemorrhages turn black, giving the term “Black Death” to the disease. An overwhelming infection of the blood may cause death in three or four days, even before other symptoms appear.

In untreated cases of bubonic plague the mortality rate is approximately 50%–60%; pneumonic plague is usually fatal if not treated within 24 hours. Such antibiotics as streptomycin and tetracycline greatly reduce the mortality rate. Vaccine is available for preventive purposes. Rodent control is important in areas of known infection.


History

The earliest known visitation of the plague to Europe may have occurred in Athens in 430 B.C., but it is unclear if the disease that afflicated Athens was caused by Yersina pestis. A disastrous epidemic occurred in the Mediterranean during the time of the Roman emperor Justinian; an estimated 25% to 50% of the population is reported to have succumbed. The most widespread epidemic began in Constantinople in 1334, spread throughout Europe (returning Crusaders were a factor), and in less than 20 years is estimated to have killed three quarters of the population of Europe and Asia. The great plague of London in 1665 is recorded in many works of literature. Quarantine measures helped contain the disease, but serious epidemics continued to occur even in the 19th cent. The disease is still prevalent in parts of Asia, and sporadically occurs elsewhere (approximately 2,500 cases worldwide annually). In Surat, India, in 1994, 5,000 cases of pneumonic plague were reported in an outbreak; an estimated 100 people died, and more than 400,000 people fled the city. Because the number of cases of plague has been increasing annually, it is categorized as a re-emerging infectious disease by the World Health Organization.












pleurisy

inflammation of the pleura (the membrane that covers the lungs and lines the chest cavity). It is sometimes accompanied by pain and coughing. The inflammation may be dry or it may be accompanied by an effusion, or fluid, that fills the chest cavity; when the effusion is infected, the condition is known as empyema. The dry type of pleurisy usually occurs in association with bacterial infections such as pneumonia. Pleurisy with effusion is often associated with such chronic lung conditions as tuberculosis or tumors. Immune disorders such as lupus and rheumatic fever tend to have recurrent pleurisy, with or without effusion. Epidemic pleurodynia, a pleurisy attributed to a virus, is a mild disease of short duration. Treatment of pleurisy is directed at the underlying condition as well as the symptoms.












pneumoconiosis

chronic disease of the lungs. Primarily an occupational disease of miners, sandblasters, and metal grinders, it is a result of repeated inhalation of dusts, including iron oxides (e.g., rust and filings), silicates (e.g., talc and rock dust), and carbonates (especially coal dust). Particles collect in the lungs and become sites for the formation of fibrous nodules. As the disease progresses, fibrous tissue increasingly replaces elastic lung tissue. Loss of lung function is signaled by shortness of breath, wheezing, coughing, and difficulty in expectorating. A heart deficiency called cor pulmonale may develop in severe cases. Sufferers are particularly vulnerable to infectious lung diseases such as tuberculosis. Pneumoconiosis is incurable and treatment is purely symptomatic. Because the inhaled dusts cause darkening of the lung tissue, the disease is also known as black lung. Silicosis, the form of the disease prevalent among miners, is commonly called miner's lung.












pneumothorax

collapse of a lung with escape of air into the pleural cavity between the lung and the chest wall. The cause may be traumatic (e.g., gunshot or stab wound), spontaneous (rupture due to disease or localized weakness of the lung lining), or environmental (extreme change in atmospheric pressure). The only symptom may be a sudden pain in the chest. Physical and radiological examination reveals characteristic signs of lung collapse. Simple pneumothorax of only one lung generally requires only rest; the break in the pleura usually heals quickly after collapse of the lung has taken place. In tension pneumothorax (where there is high intrapleural pressure), or if both lungs are collapsed, it is mandatory to remove the air from the pleural cavity immediately. An artificial pneumothorax is one deliberately induced, as in the treatment of tuberculosis of the lung before modern drugs became available, or in the diagnosis of lung disease.












pneumonia

acute infection of one or both lungs that can be caused by a bacterium, usually Streptococcus pneumoniae. or by a virus, fungus, or other organism. The causal organisms reach the lungs through the respiratory passages. Usually an upper respiratory infection precedes the disease. Alcoholism, extreme youth or age, debility, immunosuppressive disorders and therapy, and compromised consciousness are predisposing factors. When one or more entire lobes of the lung are involved, the infection is considered a lobar pneumonia. When the disease is confined to the air spaces adjacent to the bronchi, it is known as bronchopneumonia. Aspiration pneumonia is the pathological consequence of the abnormal entry of fluids, particulate matter, or secretions in the lower airways.

The symptoms of pneumonia are high fever, chills, pain in the chest, difficulty in breathing, cough, and sputum that is pinkish at first and becomes rust-colored as the infection progresses. The skin may turn bluish because the lungs are not sufficiently oxygenating the blood. Complete bed rest and good supportive care are important. Oxygen helps to relieve severe respiratory difficulty.

Immunization for pneumococcal pneumonia is recommended for children under two years old, adults 65 or older, and others at risk. Penicillin is most commonly used to treat pneumococcal pneumonia and other pneumonias caused by bacteria and, with the other antibiotic and sulfa drugs, is responsible for the marked decline since the mid-20th cent. in mortality figures. Nevertheless, pneumonia is still a serious disease, especially in elderly and debilitated persons (who usually acquire bronchopneumonia) or when complicated by bacterial invasion of the bloodstream, membranes of the heart, or the central nervous system.

Viral pneumonia, generally milder than the bacterial form, is the result of lower respiratory infection and has been the cause of more than 90% of deaths for individuals over 65. Pneumocystis carinii pneumonia, which is caused by an organism traditionally thought to be a parasitic protozoan but now suspected to be a fungus, generally only occurs in patients who have AIDS or leukemia or whose immune system is otherwise suppressed.

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