toxic shock syndrome (TSS). acute, sometimes fatal, disease characterized by high fever, nausea, diarrhea, lethargy, blotchy rash, and sudden drop in blood pressure. It is caused by Staphylococcus aureus, an exotoxin-producing bacteria (see toxin). Toxic shock was initially identified among menstruating women using high-absorbency tampons that contained synthetic materials, now no longer used, that bound and removed magnesium from the surrounding bodily environment. The resulting lower magnesium levels encouraged bacterial exotoxin production. Slightly more than half of all cases now occur in menstruating women; nonmenstruating women, men, and children may also develop TSS, as a result of infection after surgery and other causes. Treatment mainly involves supportive measures, such as intravenous fluids and, if necessary, kidney dialysis, but may include antibiotics and immunoglobulin.

sudden infant death syndrome (SIDS) or crib death, sudden, unexpected, and unexplained death of an apparently healthy infant under one year of age (usually between two weeks and eight months old). SIDS accounts for 10% of infant deaths and is the second highest cause of death (after accidents) in infancy. The risk is higher in males, in low-birth-weight infants, in lower socioeconomic levels, during cold months, and for babies who sleep face down.

Causal theories suggest that the infant may have immature or hypersensitive lungs, may have a defect in brain-stem control of breathing, or may be rebreathing carbon dioxide. Recent studies have shown persistent high levels of an infant form of hemoglobin in babies with known risk factors for the condition.

SIDS victims are thought to have brief episodes of apnea (breathing stoppage) before the fatal one. An alarm system that detects breathing abnormalities is sometimes used with infants suspected of being prone to SIDS. The American Academy of Pediatrics has recommended that babies be laid to sleep on their backs or sides.

premenstrual syndrome (PMS), any of various symptoms experienced by women of childbearing age in the days immediately preceding menstruation. It is most common in women in their twenties and thirties. Some 70%-90% of menstruating women are said to have PMS on a cyclical basis. There are over 150 symptoms associated with the syndrome, including behavioral changes, eating binges, moodiness, irritability, fatigue, fluid retention, breast tenderness, and headaches. Some women have mild symptoms; others have symptoms that interfere with work or home life. A few are completely incapacitated, a condition called premenstrual dysphoric disorder. The symptoms vary from woman to woman, and each woman's symptoms may vary from month to month, making diagnosis difficult.

The exact cause is unknown. Hormonal imbalances, nutritional deficiencies, and neurotransmitter (serotonin and norepinephrine) fluctuations are being studied. PMS patients who have had hysterectomies may continue to have symptoms, but the symptoms in all patients disappear with menopause. There is no cure for PMS. In some women, dietary changes and exercise provide some relief through the loss of water weight, the alleviation of stress, and an increase in the production of endorphins. Antidepressants or antianxiety drugs are sometimes prescribed. In severe cases hormones that induce a premature menopause may be administered.

irritable bowel syndrome (IBS), condition characterized by frequently alternating constipation and diarrhea in the absence of any disease process. It is usually accompanied by abdominal pain, especially in the lower left quadrant, bloating, and flatulence. Other symptoms, such as heartburn, lower back pain, and agitation, may be present concurrently. The cause of irritable bowel syndrome is unknown; on examination there are no physical abnormalities. The symptoms result from a disturbance of the normal peristaltic movements of the lower intestine. IBS is the most common gastrointestinal complaint in the United States. It affects twice as many women as it does men. In some individuals it is made worse by emotional stress, spicy foods, or excessive caffeine consumption. Symptoms can be minimized by a high-fiber diet and antispasmodic drugs. Acupuncture is helpful in many cases.

infant respiratory distress syndrome (IRDS) or hyaline membrane disease, respiratory distress syndrome of newborns, most common in infants born prematurely or by cesarean section or having a diabetic mother. The immature lungs of such infants cannot retain air; the air spaces empty completely and collapse after the first (and each succeeding) exhalation. Plasma leaks out of the lung tissue and coats the air spaces with a pink coating that is glassy, or hyaline, in appearance, hence the alternate name of the disease. Exhaustion, resulting from the extreme effort required to breathe, has been responsible for the death of many afflicted infants.

IRDS is caused by a lack, in the immature lung, of a surfactant agent; the substance, a mixture of lipids and proteins, contributes to the elasticity of lung tissue and stabilizes air passages so that the lung remains partly aerated after each exhalation. Intensive care, including supplemental oxygen and, in the case of severe symptoms, aid in breathing from a ventilator, can often bring infants through the first five or six days, after which most recover completely. An artificial surfactant may be introduced into the lungs if a newborn is at high risk for IRDS. If labor begins prematurely and cannot be halted and tests show that the fetus's lungs are immature, steroids administered to the mother a few days prior to labor may promote lung maturation.

fetal alcohol syndrome (FAS), pattern of physical, developmental, and psychological abnormalities seen in babies born to mothers who consumed alcohol during pregnancy. The abnormalities include low birthweight, facial deformities, and mental retardation, and there appears to be an association with impulsive behavior, anxiousness, and an inability on the part of the affected children to understand the consequences of their actions. When some but not all of these abnormalities are present, they are referred to as fetal alcohol effects (FAE). FAE has been observed in children of mothers who drank as little as two drinks per week during pregnancy. FAS affects 1 to 2 babies per 1,000 born worldwide. Many require constant lifelong supervision and end up institutionalized because of dysfunction in the family. FAS was first defined as a syndrome in 1973, although it has been observed for centuries. See also alcoholism.

chronic fatigue syndrome (CFS), collection of persistent, debilitating symptoms, the most notable of which is severe, lasting fatigue. In other countries it is known variously as myalgic encephalomyelitis, chronic fatigue and immune dysfunction syndrome, and postviral fatigue syndrome. It was first recognized as a syndrome in the 1860s by Dr. George Beard, who called it neurasthenia. He believed it to be a neurosis with a fatigue component. Definitions and theories of its cause have changed over the years; many cases have been misdiagnosed as imaginary because doctors could find no cause. In the mid-1980s it came to the public's attention, as affluent women in their thirties began to seek treatment. (For unknown reasons, more women than men seek treatment for the disease.)

Symptoms and Identification

As currently defined, chronic fatigue syndrome is the presence of severe, disabling fatigue lasting for six or more consecutive months. The fatigue is persistent or relapsing, and is new (i.e., not lifelong), not relieved by rest, not the result of ongoing exertion, and interferes with normal work, social, educational, or personal activities. Diagnosis also requires at least four of the following symptoms, each persistent or recurring and not present before the fatigue: impairment of short-term memory or concentration, sore throat, tender lymph nodes in the neck or axillary region, muscle pain, joint pain, headaches peculiar to the syndrome, unrefreshing sleep, and malaise of more than one day's duration following exertion. Chronic fatigue that does not meet all these criteria is termed "idiopathic fatigue."

The course of the disease varies. Many people first experience symptoms after a cold or bout of the flu. Most people reach a plateau early on; the symptoms come and go with varying severity afterward. Some experience complete remission; others have their symptoms indefinitely.

There are no specific diagnostic tests. Diagnosis must first rule out known causes of fatigue such as hypothyroidism, cancer, multiple sclerosis, and major depression with psychotic or melancholic features (e.g., schizophrenia, bipolar disorder). Chronic fatigue syndrome and nonpsychotic, nonmelancholic depression, however, are not mutually exclusive. Substance abuse and side effects of prescribed medications must also be eliminated as possible causes.

Cause and Treatment

There is no known single cause of CFS. Some authorities believe it is a condition shared by many different underlying diseases rather than an entity unto itself; others believe it is caused by a defect of the immune system. Hormonal deficits, low blood pressure, and viral infections have been studied as possible causes or contributors. The postulated causal link with Epstein-Barr virus hypothesized in the mid-1980s has been discounted.

There is no definitive treatment for CFS, although success has been reported anecdotally with antidepressants, antianxiety medications, antivirals, and immune boosters. Symptomatic treatment for the muscle and joint pains is helpful in some cases. Counseling and peer support groups help some patients cope with the frustrating nature of the disease.

carpal tunnel syndrome: see repetitive stress injury.

acquired immunodeficiency syndrome, see AIDS.

Reye's syndrome, rare but life-threatening disease characterized by acute encephalopathy and fatty infiltration of internal organs, especially the liver. It occurs almost entirely in children under age 15. The cause is unknown, but the disease usually follows an acute viral infection (particularly influenza or chicken pox), especially when aspirin or other salicylates have been given. The symptoms, which occur about a week after the virus infection, are vomiting and disorientation; these may be followed by seizures, coma, and respiratory arrest. Treatment is directed toward reducing brain swelling, correcting blood chemistry changes due to liver damage, and providing respiratory support if needed. Doctors recommend that children be given acetaminophen rather than aspirin for viral infections or fever.

Ménière's syndrome, disorder of the inner ear characterized by recurrent episodes of loss of balance combined with deafness and a ringing sensation. It was first described by the French otologist Prosper Ménière, in 1861. The sufferer experiences severe dizziness, in which objects may seem to spin around, and often nausea, vomiting, and sweating. Attacks may last for several hours. In the disorder, which occurs most often in men between the ages of 40 and 60, the cochlear duct of the inner ear is found to be enlarged, as a result of acoustic trauma, viral endolymphatic labyrinthitis, and ototoxic drugs. The damage produced by these factors cause lesions or disturbances in the inner ear. The disease is treated by administration of antihistamines, anticholinergic agents (e.g., atropine or scopolamine), or diuretics. Surgical procedures that relieve the condition include vestibular neurectomy, labyrinthectomy, sacculotomy (placement of a stainless steel tack through the footplate of the stapes), ultrasonic irradiation, endolymphatic-subarachnoid shunt, and cryosurgery for relief of frequent vertiginous attacks and degenerative hearing.

Gulf War syndrome, popular name for a variety of ailments experienced by veterans after the Persian Gulf War. Symptoms reported include nausea, cramps, rashes, short-term memory loss, fatigue, difficulty in breathing, headaches, joint and muscle pain, and birth defects. Ailments have been reported by American, Canadian, Australian, and British veterans alike; in some cases spouses of veterans have reported similar symptoms.

The mysterious syndrome has sparked debate between veteran's groups, congressional investigators, and the military over questions of accountability, treatment, and compensation. Hypothesized causes have included parasites, biological and chemical warfare agents, prophylactic vaccines and medications given against biological and chemical warfare agents, fumes from oil well fires, and stress. In 1994 an advisory panel organized by the National Institutes of Health reported that the syndrome represented many illnesses and many causes; they deemed biological and chemical warfare agents unlikely as causes. Causes for the illnesses in many subsets of patients have been identified, e.g., some 30 veterans had leishmaniasis, a parasitic disease spread by sand flies, but in many instances the cause has not been identified.

In 1999 researchers said that brain scans of some sick veterans revealed signs of damage caused by exposure to toxic chemicals, and a study in 2004 suggested that some veterans may have been sensitive enough to otherwise low levels of poison gases to cause symptons associated with the syndrome. A committee appointed by Congress said in 2008 that evidence suggested that acetyl cholinesterase inhibitors, which include the nerve gas sarin, an anti-nerve-gas agent, and pesticides used against sand flies, and a genetic sensitivity to such chemicals may be the cause of the syndrome. Some medical historians have pointed out that syndromes of undiagnosable diseases have occurred after other wars, including World Wars I and II and the American Civil War.

Down syndrome, congenital disorder characterized by mild to severe mental retardation, slow physical development, and characteristic physical features. Down syndrome affects about 1 in every 730 live births and occurs in all populations equally. It was first described in 1866 by an English physician, J. Langdon Down. In 1959 a French physician, Jerome Lejeune, discovered that the syndrome was caused by an extra chromosome. It was later discovered that this extra chromosome appears as a third chromosome attached to the 21st of the 23 pairs of chromosomes normally present in the human genome. This third chromosome gives rise to the alternate name trisomy 21.

The extra genetic material is responsible for the physical characteristics of the syndrome: low muscle tone, flattish facial features, an upward slant to the eyes and epicanthal folds (which were the basis for the former name, mongolism), a single crease across the palm, hyperflexibility of the joints, and a displastic middle phalanx on the fifth finger. People with Down syndrome have an increased incidence of infection, childhood leukemia, congenital heart defects, and respiratory problems, but modern medical treatment has improved the life expectancy from 9 (in 1910) to 55 (in 1995).

Mental retardation varies widely, from minimal to severe. The great majority of those who have the disorder attend public schools and as adults can live independently or in group homes. After age 35 individuals with the syndrome develop the neurological changes of Alzheimer's disease, and many develop the dementia that accompanies them.

Eighty percent of children with Down syndrome are born to women under 35 years of age, but the incidence of Down syndrome births does increase with age. Approximately 5% of cases are transmitted by the sperm. Amniocentesis or chorionic villus sampling can be used to detect the disorder in the fetus. Children born to women with Down syndrome have a 50% chance of having the disorder.

Bacterial disease caused by a toxin produced by the bacterium Staphylococcus aureus. It was first recognized in 1978 in women using superabsorbent tampons. High fever, diarrhea, vomiting, and rash may progress to abdominal tenderness, drop in blood pressure, shock, respiratory distress, and kidney failure. The syndrome also has other causes, including postsurgical infection. Antibiotics are not effective. With intensive supportive therapy, most patients recover in 7–10 days, but 10–15percnt die. Many patients have a milder recurrence within eight months.

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or crib death

Unexpected death of an apparently well infant. It occurs almost always during sleep at night and usually at 2–4 months of age. Sleeping facedown and exposure to cigarette smoke have been implicated. It is more common in cases of premature birth, low birth weight, and poor prenatal care. Many cases that would once have been labeled SIDS prove to be due to suffocation in bedding or overheating. Some babies who die of SIDS have been found to have brain stem abnormalities that interfere with their response to high levels of carbon dioxide in the blood.

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in full severe acute respiratory syndrome

Highly contagious respiratory illness characterized by a persistent fever, headache, and bodily discomfort, followed by a dry cough that may progress to great difficulty in breathing. SARS appeared in November 2002 in Guangdong province, China, and was brought to Hong Kong in February 2003. As it spread from there to other countries of East Asia and the world, health authorities instituted an unprecedented series of control measures, including quarantines and prohibitions on travel, and in June 2003 the global outbreak was declared to be contained. By that time more than 8,000 cases had been reported, and some 800 people had died. SARS is believed to be caused by a mutant coronavirus, a type usually associated with pneumonia and the common cold. A specific vaccine has not been developed. Treatment is usually restricted to easing the patient's symptoms—providing mechanical ventilation if necessary—until the illness has run its course.

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or hyaline membrane disease

Common complication in newborns, especially after premature birth. Symptoms include very laboured breathing, bluish skin tinge, and low blood oxygen levels. Insufficient surfactant in the pulmonary alveoli raises surface tension, hampering lung expansion. The alveoli collapse (see atelectasis), and a “glassy” (hyaline) membrane develops in the alveolar ducts. Once the leading cause of death in premature infants, the syndrome is now usually treated for a few days with a mechanical ventilator (see respiratory therapy), with no aftereffects. An adult respiratory distress syndrome (ARDS) can follow lung injury.

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Variable group of symptoms occurring before menstruation in 40percnt of women, severe in about 10percnt of those. Physical symptoms may include headache, cramps, bloating, and constipation or diarrhea. Emotional symptoms range from irritability, lethargy, and mood swings to hostility, confusion, and depression. Theories as to the cause centre on hormones, nutrition, and stress (known to affect severity). Depending on the symptoms, treatment may involve exercise, stress management, nutritional therapy, or drugs. Dietary measures include low sodium and high protein and complex carbohydrate intake and avoidance of xanthines (including caffeine). Increasing calcium intake has been shown to prevent or reduce cramps, which are best treated with ibuprofen.

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Sudden debilitating fatigue of unknown cause. It may follow a nonspecific illness with mild fever, tender lymph nodes, sore throat, headaches, weakness, muscle and joint pain, and confusion or difficulty in concentrating. To meet the criteria of CFS, the syndrome must be new, with a definite point of onset, and must persist more than six months. Once dismissed as imaginary, CFS remains controversial. Many authorities question whether it is a distinct disorder, since there is considerable overlap with other conditions such as fibromyalgia and Gulf War syndrome. No diagnostic test for CFS exists. Although a number of theories about the cause of CFS have been advanced, none has been proved. No cure has been found, but most patients improve gradually.

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Psychological reaction occurring after a highly stressful event and typically characterized by flashbacks, recurrent nightmares, and avoidance of reminders of the event; depression and anxiety are often present. Traumatic events that can lead to PTSD include automobile accidents, rape or assault, military combat, torture, and such natural disasters as floods, fires, or earthquakes. Long-term effects can include marital and family problems, difficulties at work, and abuse of alcohol and other drugs. Antidepressant medication and psychotherapy, including group therapy, are used in treating the disorder.

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or polycystic ovary syndrome (PCOS)

Endocrine disorder in women, characterized by high levels of male hormones (androgens) and infrequent or absent ovulation (see reproductive system). It causes a high proportion of female infertility cases. Symptoms vary but often include increased serum concentrations of androgens, insulin resistance, hirsutism, acne, and obesity. Menstruation may be irregular, absent, or excessive. The ovaries are usually enlarged and contain cysts. The disease may remain undiagnosed until a woman tries to conceive. The underlying cause is not fully understood, and no genetic mutations have been associated with the syndrome. Many women with Stein-Leventhal syndrome are at an increased risk of developing metabolic disorders such as type II diabetes or lipid disorders such as atherosclerosis at an unusually young age. Treatment attempts to reduce androgen production. Infertility may be treated with clomiphene citrate or gonadotropins to induce ovulation.

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The ability to feel sensations and pain in a limb or limbs that no longer exist. Phantom limb syndrome experienced by amputees is generally characterized by nonpainful sensations, such as the perception of movement and reception of external stimuli (e.g., touch, pressure, itch), and by painful sensations, such as the perception of burning, tingling, or shooting pains. The syndrome can be explained by map expansion neuroplasticity, in which the local brain region that once specialized in controlling the function of the amputated limb and that is reflected as a discrete “map” in the cerebral cortex of the brain is taken over by an adjacent brain map such as the face map, thereby expanding the face map. The acquisition of a part of the unused phantom map by the face map results in the perception of sensation in the amputated limb when the face is touched. Treatment of the syndrome may employ pain-relieving medications, coping techniques, nonsurgical treatments (including shock therapy and acupuncture), and implantable treatments, such as deep brain stimulation and spinal cord stimulation. Mirror box therapy has been successful in a small number of patients, primarily those who experienced paralysis of a limb prior to amputation and thus suffer from a condition known as “learned paralysis.”

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or IBS

Chronic disorder characterized by abdominal pain, intestinal gas, and diarrhea, constipation, or both. Other symptoms may include abdominal pain that is relieved after defecation or a sensation of incomplete rectal evacuation. IBS is caused by a motility disturbance of the intestines that may result from increased intestinal sensitivity to distension. Stress or the consumption of fatty foods, milk products, certain fruits or vegetables (e.g., broccoli and cabbage), alcohol, or caffeine may cause similar symptoms. Treatment includes relaxation, exercise, and avoidance of aggravating foods. Antidiarrheal medications or fibre supplements may help lessen symptoms. Although IBS may cause discomfort and emotional distress, the disorder does not result in any permanent intestinal damage.

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Various congenital disorders in a newborn caused by the mother drinking alcohol during pregnancy. The main symptoms are retarded growth, abnormalities of the central nervous system, and certain face and head abnormalities. The child may be mentally retarded. Behavioral problems (e.g., poor concentration, impulsiveness) are sometimes the only obvious symptoms. The syndrome is common in babies born to chronic alcoholics, but health care organizations now commonly recommend that women cease drinking alcohol entirely while pregnant. Other disorders have been linked to alcohol in breast milk.

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Painful condition caused by repetitive stress to the wrist over time. The median nerve and the tendons that bend the fingers pass through the carpal tunnel on the inner side of the wrist, between the wrist (carpal) bones on three sides and a ligament on the fourth. Repetitive finger and wrist movements rub the tendons against the walls of the carpal tunnel and may make the tendons swell, squeezing the nerve. Numbness, tingling, and pain in the wrist and hand may progress to loss of muscle control. CTS is most common in assembly-line workers and computer keyboard users. Treatment may include avoidance of the causative activity, ergonomic workplace design, anti-inflammatory drugs, brace or splint use, and surgery.

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Crime of inflicting physical or emotional injury on a child. The term can denote the use of inordinate physical violence or verbal abuse; the failure to furnish proper shelter, nourishment, medical treatment, or emotional support; incest, rape, or other instances of sexual molestation; and the making of child pornography. Child abuse can cause serious harm to its victims. Estimates of the numbers of children who suffer physical abuse or neglect by parents or guardians range from about 1 percent of all children to about 15 percent, and figures are far higher if emotional abuse and neglect are included. In many cases, the abuser himself suffered abuse as a child. When abuse results in death, evidence of child abuse or battered-child syndrome (e.g., broken bones and lesions, either healed or active) is often used to establish that death was not accidental.

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in full acquired immunodeficiency syndrome

Transmissible disease of the immune system caused by HIV. AIDS is the last stage of HIV infection, during which time the individual develops frequently fatal infections and cancers, including Pneumocystis carinii pneumonia, cytomegalovirus (CMV), lymphoma, and Kaposi sarcoma. The first AIDS cases were identified in 1981, HIV was isolated in 1983, and blood tests were developed by 1985. According to the UN's 2004 report on AIDS, some 38 million people are living with HIV, approximately 5 million people become infected annually, and about 3 million people die each year from AIDS. Some 20 million people have died of the disease since 1981. Sub-Saharan Africa accounts for some 70 percent of all HIV infections. Rates of infection are lower in other parts of the world, but the epidemic is spreading rapidly in eastern Europe, India, South and Southeast Asia, Latin America, and the Caribbean.

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Chromosomal disorder (from the presence of only one sex chromosome, X, in all or some of the body's cells) that causes abnormal sexual development in females. The syndrome may include absent or undeveloped ovaries, underdeveloped secondary sex characteristics, low hairline, webbed neck, shield-shaped chest with wide-spaced nipples, and kidney and heart malformations with coarctation (narrowing) of the aorta. It may not be recognized until a girl fails to undergo puberty at a normal age. Estrogen treatment results in puberty, adult appearance, and normal sex drive but not fertility. Surgery can correct malformations.

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Acute neurological illness in children, following influenza, chickenpox, or other viral infections. Vomiting, lethargy, and confusion begin as the child appears to be recovering. These symptoms are followed hours or days later by drowsiness, disorientation, seizures, respiratory arrest, and coma. At worst, the syndrome includes fatty liver degeneration and potentially fatal brain swelling. There is no specific cure, but treatment of imbalances helps over 70percnt of patients survive (some with brain damage). The incidence has decreased since the recognition that it often follows use of aspirin or other salicylic acid derivatives in children during a viral illness. It can also result from aflatoxin or warfarin poisoning.

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Rare hereditary disorder of connective tissue. Affected persons are tall, with long, thin limbs and spiderlike fingers (arachnodactyly). The lens of the eye is dislocated, and many have glaucoma or detached retina. Heart muscle abnormalities and various malfunctions and malformations occur; rupture of the aorta is the most common cause of death. Severity varies; affected individuals may die young or live essentially normal lives. The underlying abnormality cannot be cured, but some of the defects can be surgically corrected.

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Cluster of illnesses in veterans of the Persian Gulf War (1990–91). These illnesses are characterized by variable and nonspecific symptoms such as fatigue, muscle and joint pains, headaches, memory loss, and posttraumatic stress reactions. It is believed to be caused by exposure to chemicals called anticholinesterases, which are found in nerve toxins, insecticides, and prophylactic anti-nerve toxin drugs. The disorder does not appear to be fatal but can be associated with considerable distress and disability.

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or trisomy 21

Congenital disorder caused by an extra chromosome (trisomy) on the chromosome 21 pair. Those with the syndrome may have broad, flat faces; up-slanted eyes, sometimes with epicanthal folds (whence its former name, mongolism); intellectual disability (usually moderate); heart or kidney malformations; and abnormal fingerprint patterns. Many persons with Down syndrome can live and work independently or in a sheltered environment, but they age prematurely and have a short (55-year) life expectancy. The risk of bearing a child with the disorder increases with the mother's age; it can be detected in the fetus by amniocentesis.

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