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Familial Mediterranean fever is a hereditary disorder characterized by episodes of high fever with abdominal pain or, less commonly, chest pain, joint pain, or a rash.
Familial Mediterranean fever occurs most commonly among people of Mediterranean origin (such as Sephardic Jews, Arabs, Armenians, and Turks). Most of these people have family members who have had the disorder (family history). However, in the United States, about 50% of people with familial Mediterranean fever have no known family history of the disorder.
Familial Mediterranean fever is caused by an abnormal recessive gene (see Genetics: Recessive Disorders). That is, to develop the disorder, people must have two copies of the abnormal gene, one from each parent. The abnormal gene results in the production of a defective form of pyrin, a protein that regulates inflammation.
If not treated adequately, some people with familial Mediterranean fever develop amyloidosis. In amyloidosis, an unusually shaped protein called amyloid is deposited in the kidneys and in many organs and tissues, impairing their function (see Amyloidosis).
Symptoms
Symptoms usually begin between the ages of 5 and 15. Attacks of abdominal pain occur in about 95% of people. Attacks happen irregularly and are accompanied by fever as high as 104° F (40° C). The painful attacks usually last 24 to 72 hours but occasionally last as long as a week. Attacks may occur as often as twice a week or as seldom as once a year. The severity and frequency of the attacks tend to decrease with age and during pregnancy. Sometimes the attacks stop completely for a number of years, only to resume later. Some people have warning symptoms before the attacks begin.
The abdominal pain is caused by inflammation of the lining of the abdominal cavity (peritonitis). The pain usually starts in one part of the abdomen, then spreads throughout the entire abdomen. The severity of the pain may vary with each attack.
In the United States, certain symptoms are less common among affected people:
If amyloidosis affects the kidneys, people may retain fluids, feel weak, and lose their appetite.
About one third of women with the disorder are infertile or miscarry. The disorder can cause scar tissue to form in the abdomen. The scar tissue can interfere with conception.
Despite the severity of symptoms during attacks, people rapidly recover and remain free of illness until their next attack. However, without treatment, the amyloid deposits may damage the kidneys, eventually resulting in kidney failure.
Diagnosis
A doctor usually bases the diagnosis on typical symptoms. However, the abdominal pain of familial Mediterranean fever is virtually indistinguishable from that of other abdominal emergencies, particularly a ruptured appendix. Thus, some people with this disorder have urgent surgery before the correct diagnosis is made.
No routine laboratory test or imaging test is by itself diagnostic, but such tests can be useful in excluding other disorders. Blood tests can identify some of the abnormal genes that cause this disorder and can thus sometimes help with the diagnosis.
Prevention and Treatment
Taking colchicine daily by mouth eliminates or greatly reduces the number of painful attacks in about 85% of people. Also, it virtually eliminates the risk of kidney failure due to amyloidosis. If people have infrequent attacks preceded by warning symptoms, they can wait until symptoms start before they take colchicine, but they must then take it promptly.
Although mild analgesics, such as nonsteroidal anti-inflammatory drugs (NSAIDs) may relieve pain sufficiently, opioids, such as meperidine, are usually needed.
Last full review/revision January 2009 by Stephen E. Goldfinger, MD
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