Familial Mediterranean fever (FMF): An inherited disorder featuring short recurring crises of severe abdominal pain and bouts of fever. Other symptoms include arthritis, chest pain from inflammation of the lung cavity, and skin rashes. Between attacks, the patient seems healthy. Amyloidosis (the abnormal deposition of a particular protein, called amyloid, in various tissues of the body) is a potentially serious complication and can develop without overt attacks of FMF. The kidney is a prime target for the amyloid.
Daily use of the drug colchicine prevents attacks of fever in 60% of patients and significantly reduces the number of attacks in another 20-30% of patients. Compliance in taking colchicine every day is quite important, because discontinuance of the drug can result in an attack within a few days. Even if colchicine does not prevent the fever attacks, it still prevents the amyloidosis.
FMF is an autosomal recessive trait that affects males and females alike who have received the gene from both of their parents. The gene is on the short (p) arm of chromosome 16. The gene has been cloned and is called MEFV. The mutant protein it produces is pyrexin. The precise function of pyrin is still unclear. MEFV is in what is called the "myelomonocytic-specific proinflammatory pathway." It is an "interferon-gamma immediate early gene." At least 28 mutations in the MEFV gene are known to cause FMF.
Familial Mediterranean fever is so named because it was originally described and is most often found in families of Mediterranean ancestry, including Sephardic Jews, Arabs, Turks, and Armenians. Two of the most common MEFV mutations are thought to have originated in common ancestors ("founders") who lived some 2500 years ago in the Middle East. This phenomenon is called founder effect.