Objective: A number of differences have been noted in clinical familial Mediterranean fever (FMF) among ethnic groups. Iraqi Jews and Druzes are characterized by less severe disease. The differences in disease expression raise the possibility of background genes peculiar to specific ethnic groups.
Methods: We analyzed a series of FMF linked microsatellite markers and searched for gene mutations in these 2 populations.
Results: We observed a conserved haplotype in 46% of the FMF druze chromosomes that was different from the Mediterranean haplotype but identical to the ARM3 haplotype. In contrast, 56% of the FMF chromosomes in Iraqi Jews displayed the same mutation as that found in Jews from North Africa.
Conclusion: Variable expression in FMF is probably due to both allelic heterogeneity and/or modifier genes as well as environmental factors.