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 see 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 see Amyloidosis).
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 may last longer. Attacks may occur as often as twice a week or as seldom as once a year. The severity and frequency of the attacks may decrease with age, during pregnancy, and in patients who develop amyloidosis. Sometimes the attacks stop completely for a number of years, only to resume afterwards.
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.
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. About 20 to 30% or pregnancies end in loss of the fetus. The disorder can cause scar tissue to form in the pelvis. 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, amyloid deposits may damage the kidneys, eventually resulting in kidney failure.
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 the abnormal gene that causes this disorder and can thus sometimes help with the diagnosis. Some people with typical familial Mediterranean fever have only one rather than two copies of the gene, and in others, test results may be negative.
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. In pregnant women, colchicine helps prevent attacks that might lead to a miscarriage. If people have infrequent attacks that begin slowly, they can wait until symptoms start before they take colchicine, but they must then take it promptly.
If colchicine is ineffective, other drugs such as infliximab, given intravenously, or anakinra or rilonacept, injected under the skin, may help. These drugs modify how the immune system functions and thus help reduce inflammation
Last full review/revision July 2013 by Stephen E. Goldfinger, MD