The NM_000152.5:c.1099del (p.Trp367GlyfsTer25) variant in GAA is a nonsense variant predicted to cause a premature stop codon, leading to nonsense mediated decay in a gene in which loss-of-function is an established disease mechanism (PVS1). This variant is not in gnomAD v2.1.1. ( PM2_Supporting). To our knowledge, this variant has not been reported in patients with Pompe disease in the literature, and results of functional studies are not available. There is a ClinVar entry for this variant (Variation ID: 370810). The classification of this variant has been upgraded from Variant of Uncertain Significance to Likely Pathogenic based on the recommendations of the ClinGen Sequence Variant Interpretation Working Group, that a variant meeting PVS1 and PM2_Supporting is classified as Likely Pathogenic (https://clinicalgenome.org/site/assets/files/5182/pm2_-_svi_recommendation_-_approved_sept2020.pdf ). In summary, this variant meets the criteria to be classified as likely pathogenic for Pompe disease. GAA-specific ACMG/AMP criteria applied, as specified by the ClinGen LSD VCEP (Specifications Version 2.0): PVS1, PM2_Supporting. (Classification approved by the ClinGen Lysosomal Diseases VCEP, March 10, 2023).