The NM_005629.4:c.1A>G p.(Met1Val) variant in SLC6A8 variant in SLC6A8 may cause a truncated or absent protein by altering the start codon of the coding sequence and is predicted to lead to the omission of a critical region of the protein (PVS1_Moderate). The variant was identified in a family with increased urinary creatine to creatinine ratio; additional details not provided (PMID: 23644449) (PP4). This variant is absent from gnomAD v2.1.1, therefore PM2_Supporting criteria is applicable. At the time of this curation, this variant has not been reported in individuals with suspected Creatine Transporter Deficiency in the literature. In summary, this variant meets the criteria to be classified as a Variant of Uncertain Significance for Creatine Transporter Deficiency based on the ACMG/AMP criteria applied, as specified by the ClinGen Cerebral Creatine Deficiency Syndromes Variant Curation Expert Panel (Specifications Version 1.0): PVS1_Moderate, PP4, PM2_Supporting. (Classification approved by the ClinGen Cerebral Creatine Deficiency Syndromes Variant Curation Expert Panel on March 23, 2023).