MEFV and familial Mediterranean fever: If heterozygosity played a significant role in FMF occurrence, the observed prevalence (P) should stand in between q2<P<2pq+q2 (q: frequency of mutated MEFV alleles; p: frequency of normal MEFV alleles; q2: frequency of individuals carrying two mutated alleles; 2pq: frequency of heterozygotes).