ClinVar

Description

Variant summary: MEFV c.329T>C (p.Leu110Pro) results in a non-conservative amino acid change in the encoded protein sequence. Four of five in-silico tools predict a benign effect of the variant on protein function. The variant allele was found at a frequency of 0.0066 in 247780 control chromosomes, predominantly at a frequency of 0.084 within the East Asian subpopulation in the gnomAD database, including 61 homozygotes. The observed variant frequency within East Asian control individuals in the gnomAD database is approximately 4-fold of the estimated maximal expected allele frequency for a pathogenic variant in MEFV causing Familial Mediterranean Fever phenotype (0.022), strongly suggesting that the variant is a benign polymorphism found primarily in populations of East Asian origin. However, the variant c.329T>C has also been commonly reported in FMF patients, primarily in the same allele (in cis) with p.E148Q, both in heterozygote and homozygote phases. In addition, multiple publications show lack of cosegregation for the variant and disease (Oshima_2010, Berdeli_2011, and Kim_2007). In Japanese population, the variant's allele frequency is higher in patients than in controls. Case-control studies in Japanese population indicate this variant may associate with increased risk of FMF (OR= 1.78, Migita_2016; OR=4.81, Tsuchiya-Suzuki_2009). Larger case-control studies are needed to validate these findings. At least one functional study demonstrated no damaging effect of this variant (Honda_2021). Three ClinVar submitters (evaluation after 2014) cite the variant as benign/likely benign and three ClinVar submitters (evaluation after 2014) cite it as uncertain significance. In 2018, the experts international study group for systemic autoinflammatory diseases (INSAID) reported a validated classification of uncertain significance for the variant (Van Gijn_2018). Based on the data available at this time, it is unknown whether this variant represents a low penetrance mild common pathogenic variant, modifier, or a risk allele. Therefore, this variant was classified as uncertain significance, until additional information becomes available.