The c.1A>G (p.Met1Val) variant in ABCD1 may cause a truncated or absent protein by altering the start codon of the coding sequence (PVS1_Moderate). At least one patient with this variant displayed a primary adrenal insufficiency and increased plasma VLCFAs, which is highly specific for X-linked adrenoleukodystrophy (PP4; PMID:22176151). This variant has been reported in six more male probands meeting with a primary adrenal insufficiency and increased VLCFA ratios (PS4; PMID:34946879). This variant is absent from gnomAD v2.1.1, v3.1.2 and v4.1.0 (PM2_Supporting). Immunoblotting in transformed clonal cell lines showed severely reduced expression indicating that this variant impacts protein function. Beta-oxidation assay in transformed clonal cell lines showed the variant activity to be about 19.6% of wild type activity indicating that this variant impacts protein function (PMID:27067449, PS3_Supporting). In summary, this variant meets the criteria to be classified as likely pathogenic for X-linked adrenoleukodystrophy based on the ACMG/AMP criteria applied, as specified by the ClinGen Peroxisomal Disorders VCEP: PVS1_Moderate, PS4, PP4, PM2_Supporting, PS3_Supporting (ClinGen Peroxisomal Disorders Expert Panel Specifications to the ACMG/AMP Variant Interpretation Guidelines for ABCD1 Version 1.0.0)