The NM_000156.6:c.689C>T variant in GAMT is a missense variant in exon 6, predicted to result in the substitution of threonine for methionine at amino acid 230 (p.Thr230Met). The highest population minor allele frequency in gnomAD v2.1.1 is 0.0001308 (4/ 30576) in the South Asian population, which is lower than the ClinGen CCDS VCEP’s threshold for PM2_Supporting (<0.0004), meeting this criterion (PM2_Supporting). The computational predictor REVEL gives a score of 0.48 which is below the threshold of 0.5, evidence that does not predict a damaging effect on GAMT function (BP4). To our knowledge, this variant has not been reported in published literature in individuals with GAMT deficiency, and the results of functional studies are unavailable. This variant has been previously reported in ClinVar (Variation ID: 205595). In summary, this variant meets the criteria to be classified as a variant of uncertain significance for GAMT deficiency. GAMT-specific ACMG/AMP codes met, as specified by the ClinGen Cerebral Creatine Deficiency Syndromes VCEP (Specifications Version 1.1.0): PM2_Supporting, BP4. (Classification approved by the ClinGen CCDS VCEP on June 6, 2022).