The c.6644C>A (NM_004958.4) variant in MTOR is a missense variant predicted to cause substitution of (p.Ser2215Tyr). This variant is absent from gnomAD v2.1.1 (PM2_Supporting). MTOR, in which the variant was identified, is defined by the ClinGen Brain Malformations Expert Panel as a gene that has a low rate of benign missense variation and where pathogenic missense variants are a common mechanism of disease (PP2). A different amino acid change (p.Ser2215Phe), at this locus, is classified as pathogenic for Overgrowth with or without cerebral malformations due to abnormalities in MTOR-pathway genes by the ClinGen BMEP (PM5). This variant has been shown to significantly increase phosphorylation levels in experiments with case and controls cells of similar isogenic backgrounds indicating that this variant impacts protein function (PMIDs: 20190810, 24631838, 28963468) (PS3_Supporting). The prevalence of the variant in affected individuals is significantly increased compared with the prevalence in controls (PS4; PMID: 27830187, 29281825, 225401301, 26619011; identified in 5 individuals with neuropathology confirmatory of a malformation of cortical development, 1 individual with neuroimaging appearance consistent with a malformation of cortical development (without neuropathology), 1 individual with neuroimaging demonstrating at least one large cerebral hemisphere with cortical malformation(s), 15 tumor samples in the literature and COSMIC). Testing of unaffected and affected tissue show variable allelic fractions consistent with a post-zygotic event (PS2_Moderate; PMID: 26018084). In summary, this variant meets the criteria to be classified as Pathogenic for mosaic autosomal dominant overgrowth with or without cerebral malformations due to abnormalities in MTOR-pathway genes based on the ACMG/AMP criteria applied, as specified by the ClinGen Brain Malformations Expert Panel: PM2_P, PP2, PM5, PS3_P, PS4, PS2_M; 11 points (VCEP specifications version 1; Approved: 1/31/2021)