ClinVar

Description

Variant summary: GAA c.761C>T (p.Ser254Leu) results in a non-conservative amino acid change located in the Galactose mutarotase, N-terminal barrel domain (IPR031727) of the encoded protein sequence. Five of five in-silico tools predict a damaging effect of the variant on protein function. The variant allele was found at a frequency of 0.00019 in 282470 control chromosomes, predominantly at a frequency of 0.0028 within the East Asian subpopulation in the gnomAD database. This frequency is not significantly higher than estimated for a pathogenic variant in GAA causing Glycogen Storage Disease, Type 2 (Pompe Disease) (0.00019 vs 0.0042), allowing no conclusion about variant significance. c.761C>T has been reported in the literature as a complex allele in cis with c.752C>T (p.Ser251Leu) in settings of newborn screening for Glycogen Storage Disease, Type 2 (Pompe Disease) (example, Labrousse_2010, Chien_2011, Liao_2014). This complex allele has been observed as a homozygous and compound heterozygous genotype in the ascertained reports among newborns with screening enzyme activity below the cutoff value (example, Liao_2014). These report(s) do not provide unequivocal conclusions about association of the variant in isolation with Glycogen Storage Disease, Type 2 (Pompe Disease). Co-occurrences of this complex allele in cis with other pathogenic variant(s) have been reported in the literature (GAA c.1411_1414del , p.E471PfsX5), providing supporting evidence for a benign role (example, Larousse_2010, Liao_2014). To our knowledge, no variant specific experimental evidence demonstrating an impact on protein function has been reported. Eight clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar after 2014 without evidence for independent evaluation. Multiple laboratories reported the variant with conflicting assessments (VUS, n=2; P/LP, n=6). Based on the evidence outlined above, the variant was classified as uncertain significance.