MEFV and familial Mediterranean fever: Finally, our findings revealed a correlation between levels of inflammatory cytokines, namely, IL-1β, IL-1α, IL-6, IL-17, and IL-22 and penetrance of MEFV mutations; cytokine production was increased in M694V homozygous FMF patients when compared to those heterozygous for the same mutation or with other genotypes, suggesting that the wide clinical variability observed in FMF patients is partly related to the penetrance of MEFV mutations and allelic heterogeneity (20, 35).