Genotype-phenotype correlation in FMF patients: A “non classic” recessive autosomal or “atypical” dominant autosomal inheritance?

BACKGROUND: Uncertainty remains on the pathogenetic mechanisms, model of inheritance as well as genotype-phenotype correlation of FMF disease. OBJECTIVE: To investigate the impact of genetic factors on the FMF phenotype and the disease inheritance model. METHODS: A total of 107 FMF patients were enrolled. Patients were diagnosed clinically. All patients underwent genetic analysis of the FMF locus on 16p13.3. RESULTS: 9 distinct mutations were detected. Specifically, the 85.98% of patients showed a heterozygous genotype. The most common genotypes were p.Met680Ile/wt and p.Met694Val/wt. The most frequent clinical findings were fever, abdominal pain, joint pain, thoracic pain, and erysipelas-like erythema. Analysis of clinical data did not detect any significant difference in clinical phenotype among heterozygous, homozygous as well as compound homozygous subjects, further supporting the evidence that, contrary to the recessive autosomal inheritance, heterozygous patients fulfilled the criteria of clinical FMF. Moreover, subjects with p.Met694Val/wt and p.Met680Ile/wt genotype reported the most severe clinical phenotype. p.Ala744Ser/wt, p.Glu148Gln/Met680Ile, p.Met680Ile/Met680Ile, p.Met680Ile/Met694Val, p.Pro369Ser/wt, p.Met694Ile/wt, p.Glu148Gln/Glu148Gln, p.Lys695Arg/wt resulted in 100% pathogenicity. CONCLUSIONS: The existence of a "non classic" autosomal recessive inheritance as well as of an "atypical" dominant autosomal inheritance with incomplete penetrance and variable expressivity cannot be excluded in FMF.