Serum amyloid A1 genotype associates with adult-onset familial Mediterranean fever in patients homozygous for mutation M694V.

OBJECTIVES: FMF shows considerable variability in severity and type of clinical manifestations by geographic region, which are attributed to Mediterranean fever (MEFV) gene allelic heterogeneity, additional genetic modifiers and environmental factors. Considering the severe impact of MEFV mutation M694V on the FMF phenotype, this work aimed at investigating a possible disease modifying role of the serum amyloid A1 (SAA1) genotype in a cohort of 386 Armenian FMF patients homozygous for MEFV mutation M694V.

METHODS: A cohort of 386 Armenian patients diagnosed with FMF based on the Tel-Hashomer criteria and carrying two MEFV M694V mutant alleles were included in this study. Fifty-two (13.40%) of these patients experienced their first attack at the age of ≥20 years (i.e. adult-onset FMF). MEFV and SAA1 analyses were performed by a commercial reverse-hybridization assay, and resulting genotypes were matched against the patients' clinicodemographic profiles.

RESULTS: Genotypic distribution of SAA1 alleles was significantly different between patients with an age of onset <20 and ≥20 years. SAA1 genotypes α/α, α/β and β/β could be identified in 8 (15.38%), 12 (23.08%) and 32 (61.54%) adult-onset patients while this was the case for 47 (14.07%), 172 (51.50%) and 115 (34.43%) patients with a disease onset <20 years, respectively (P < 0.001). Furthermore, adult-onset disease was associated with a less severe FMF phenotype (P < 0.001).

CONCLUSION: We have identified a significant relationship between the SAA1β/β genotype and the age of disease onset in M694V homozygous FMF patients.