ClinVar

Description

Variant summary: GAA c.-2C>T is located in the untranslated mRNA region upstream of the initiation codon. 4/4 computational tools predict no significant impact on normal splicing. However, these predictions have yet to be confirmed by functional studies. The variant allele was found at a frequency of 0.001 in 247028 control chromosomes, predominantly at a frequency of 0.008 within the South Asian subpopulation in the gnomAD database, including 5 homozygotes. The observed variant frequency within South Asian control individuals in the gnomAD database is approximately 2-fold of the estimated maximal expected allele frequency for a pathogenic variant in GAA causing Glycogen Storage Disease, Type 2 (Pompe Disease) phenotype (0.0042), strongly suggesting that the variant is a benign polymorphism found primarily in populations of South Asian origin. To our knowledge, no occurrence of c.-2C>T in individuals affected with Glycogen Storage Disease, Type 2 (Pompe Disease) and no experimental evidence demonstrating its impact on protein function have been reported. Two clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar after 2014 without evidence for independent evaluation, and both of them classified the variant as likely benign. Based on the evidence outlined above, the variant was classified as benign.