ClinVar

Description

Variant summary: MEFV c.1223G>A (p.Arg408Gln) results in a conservative amino acid change located in the B-box-type zinc finger (IPR000315) of the encoded protein sequence. Five of five in-silico tools predict a benign effect of the variant on protein function. A recent report utilizing the meta predictor tool, REVEL (Rare Exome Variant Ensemble Learner) to assess the pathogenicity of MEFV variants with ambiguous classification proposed a likely benign outcome for this variant (Accetturo_2019). In this study, REVEL scores demonstrated a good correlation with the consensus classification of the International Study Group for Systemic Auto Inflammatory Diseases. The observed variant frequency within East Asian control individuals in the gnomAD database is approximately 2.45 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. When examined across all populations represented in the gnomAD database, the variant did not exceed the estimated maximal expected allele frequency for a disease causing MEFV allele however, in the European sub-cohort, 20 homozygous occurrences were observed, suggesting a benign nature for the variant across ethnicities. c.1223G>A has been extensively reported in databases and in the literature in individuals affected with Familial Mediterranean Fever or unexplained fevers, frequently as part of a haplotype with p.P369S (example, Ryan_2010, Migita_2014, Stoffels_2014, Pieri_2015, Hageman_2019). These report(s) do not provide unequivocal conclusions about association of the variant with Familial Mediterranean Fever. This haplotype has been reported in the homozygous state in controls as well (3 occurrences in 1000G) supporting the neutral nature of the complex allele. In two families (Feng 2009), the variant or its complex with P369S was shown to not co-segregate in all affected family members. The complex variant was also found in compound heterozygous state with a known pathogenic variant in unaffected parents (Moussa_2013). At-least one functional study further supports a neutral nature for the variant. This substitution is located in exon 3 encoding a B-box domain and is necessary for interactions with proline serine threonine phosphatase interacting protein 1 (PSTPIP1) (Ryan_2010). The ability of the MEFV to bind PSTPIP1 was not affected by the variant in isolation or as a part of a complex allele. Additionally, in silico structural modeling predicted that the variant does not result in alteration to the secondary structure elements potentially required to maintain the structural integrity of the B-box domain (Ryan_2010). Multiple clinical diagnostic laboratories and the Gene Reviews database have submitted clinical-significance assessments for this variant to ClinVar after 2014 without evidence for independent evaluation. These submitters have reported the variant with conflicting assessments ranging from Likely Benign (n=3), Uncertain Significance (n=5), Likely Pathogenic (n=2) to Pathogenic (n=1). Of note, one of these submitters has recently re-evaluated this variant from Likely Pathogenic to a VUS but not updated their ClinVar record. We have considered their assessment as a VUS in this context. Some submitters have provided overlapping evidence utilized in the context of our evaluation. We have followed this variant for over four years and previously classified it as a VUS-possibly benign variant. In our review of published evidence spanning over 20 years (1999-2019), the majority of evidence appears to point toward a non-pathogenic outcome however more data is required to conclusively determine the clinical consequences of this variant. Therefore, based on the evidence outlined above, this variant in isolation retains its classification as likely benign.