Background:Familial Mediterranean fever (FMF) is an autoinflammatory disease that is caused by Mediterranean fever (MEFV) gene mutations. It is characterized by recurrent and self-limiting febrile attacks within a short period. Although the pathologic significance ofMEFVexon 2 or exon 3 common variants in patients with FMF is modest and these variants are usually associated with less severe clinical presentations of FMF (1, 2), their combined effects with pathogenic mutation in exon 10 remain to be evaluated.Objectives:To determine the combined effect of common variants on clinical manifestations and inflammasome activity, we compared the clinical and laboratory characteristics between the coexistence and non-coexistence ofMEFVexon 2 or exon 3 variants in patients with FMF that had a heterozygousMEFVexon 10 mutation.Methods:We excluded patients with FMF that had twoMEFVexon 10 mutations in one or more alleles and those withMEFVvariants in exons other than in exons 2, 3, or 10. Finally, we reviewed 131 Japanese patients with FMF that had a heterozygousMEFVexon 10 mutation, and they were divided into the groups with and withoutMEFVexon 2 or exon 3 variants of 34 and 97, respectively. All enrolled patients had only a heterozygous M694I mutation in exon 10 of theMEFVgene. We measured serum IL-18 levels at remission without febrile attacks in the groups with and withoutMEFVexon 2 or exon 3 variants of 9 and 31, respectively.Results:In the univariate analysis, the group with variants in exon 2 or exon 3 had significantly earlier onset (16.0 years v.s. 20.5 years, p = 0.04), a higher percentage of thoracic pain with febrile attacks (68% v.s. 44%, p = 0.02), a higher frequency of attack (1.0/month v.s. 0.5/month, p = 0.02), and a higher IL-18 level in the serum at remission (606.3 pg/ml v.s. 168.4 pg/ml, p = 0.04, Figure 1) compared to the group without these variants. Importantly, multivariate analyses showed that the coexistence ofMEFVexon 2 or exon 3 variants and an exon 10 mutation was independently and significantly associated with earlier onset of FMF (p = 0.049) and thoracic pain (p = 0.03).Figure 1.Conclusion:Our results suggest that the coexistence ofMEFVexon 2 or exon 3 variants and aMEFVexon 10 mutation has combined effects on inflammasome activation in the Japanese population.References:[1]Migita K, Uehara R, Nakamura Y, et al. Familial Mediterranean fever in Japan. Medicine (Baltimore). 2012 Nov;91(6):337-43.[2]Shinar Y, Livneh A, Langevitz P, Genotype-phenotype assessment of common genotypes among patients with familial Mediterranean fever. J Rheumatol. 2000;27(7):1703.Disclosure of Interests:None declared
Familial Mediterranean fever mutations lift the obligatory requirement for microtubules in Pyrin inflammasome activation
