Familial Mediterranean fever (FMF) is a genetic disease, characterized by attacks of fever and painful manifestations. Several vasculitides are more common in FMF than in the general population. The aim of the study was to define and characterize the association between FMF and Behcet's disease (BD), a form of vasculitis not previously related to FMF.
We conducted a retrospective study in which FMF patients, also suffering from BD (FMF-BD), were recruited from about 4,000 patients registered in our clinic, using a computer survey. Patients identified by the screening process were examined, and those meeting the published criteria for the diagnoses of FMF and BD were classified as FMF-BD cases and compared with unselected FMF and BD controls.
The prevalence of BD was higher in FMF than in populations known to be rich in BD (eg, 16 per 4,000 in FMF compared with 1 per 104 in Japan, P < .001). FMF-BD cases and FMF or BD controls were comparable in most demographic, clinical, and laboratory aspects studied. However, more cases than FMF-controls were of Iraqi/Turkish origin and responded less favorably to colchicine. A higher proportion of cases than BD controls had skin, central nervous system, and gastrointestinal manifestations, originated from North Africa, and had family history of BD. In most cases, as in most respective controls, the severity of FMF was of intermediate grade and the extensiveness of BD was limited. The HLA B5 antigen was present in 53% of BD cases and 40% of BD controls.
BD should be included among the vasculitides complicating FMF. BD and FMF in patients with FMF-BD, and in patients suffering from each of these entities alone, are clinically and demographically comparable.