Familial Mediterranean fever is caused by a gene inherited from both parents.
Typically, most people have attacks of severe abdominal pain and a high fever.
The diagnosis usually is based on symptoms, but genetic testing is available.
This disorder may cause amyloidosis if not adequately treated.
Colchicine is taken to reduce or eliminate the number of painful attacks and eliminate the risk of kidney failure due to amyloidosis.
Familial Mediterranean fever is the most common hereditary periodic fever syndrome across all age groups. It occurs most commonly among people of Mediterranean origin (such as Sephardic Jews, North African Arabs, Armenians, Greeks, Italians, and Turks). However, this disorder has occurred among people of other origins (such as Ashkenazi Jews, Cubans, and Japanese). Up to 50% of people who have familial Mediterranean fever have family members, usually siblings, who have the disorder (family history).
Familial Mediterranean fever is caused by an abnormal recessive gene. That is, to develop the disorder, people usually must have two copies of the abnormal gene, one from each parent. However, rarely, only one copy of the abnormal gene may be enough to cause some symptoms.
The abnormal gene results in the production of a defective form of pyrin, a protein that regulates inflammation. There are a number of different possible mutations of the gene, not all of which have been identified, which may explain why some people with typical familial Mediterranean fever are not found to have a mutation in the gene. Alternatively, there may also be nongenetic and environmental factors that play a role in how this syndrome develops.
Symptoms of familial Mediterranean fever usually begin between the ages of 5 and 15.
The most common symptoms are
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 people 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.
Less common symptoms include
Arthritis: About 25% of people have inflammation of large joints (arthritis), such as the knees, ankles, and hips.
Rash: A painful red rash that usually appears near the ankles may occur but is comparatively rare among affected people in the United States.
Scrotum pain: In males, the thick-skinned sac that surrounds and protects the testes (scrotum) may swell and be painful due to inflammation of a testis (testicle).
Despite the severity of symptoms during attacks, people rapidly recover and remain free of illness until their next attack.
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.
Amyloid deposits may damage the kidneys, eventually resulting in kidney failure. 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% of 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.
A doctor usually bases the diagnosis of familial Mediterranean fever 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. Because some people with typical familial Mediterranean fever have only one rather than two copies of the gene or occasionally have no detectable mutations in the gene, genetic test results may be negative. In these cases, people should receive genetic counseling and care from specialists who are experienced with familial Mediterranean fever.
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 canakinumab, anakinra, or rilonacept, injected under the skin, may help. These drugs modify how the immune system functions and thus help reduce inflammation.
Ibuprofen or acetaminophen can be given to relieve pain and fever.