Unusual immunologic findings in familial Mediterranean fever.

Familial Mediterranean fever (FMF) is an inherited disease of unknown etiology. We report a case in which, during an acute febrile attack, rheumatoid factor and immunoglobulin levels rose, and the levels of complement components fell. The level of urinary fibrinogen degradation products also increased, and all results of tests returned to normal at the end of the acute attack. This suggests that an immunologic phenomenon may play a substantial role in the etiology of FMF.