The c.506C>T variant in the PDHA1 gene is a missense mutation occurring in a hotspot domain (aa position A169, located in α β heterodimer interface (PM1). This variant is absent from population databases (PM2). This variant has been reported in three individuals in the literature with presentations consistent with PDHA1-related disease. These three cases include two assumed de novo cases (PMID: 20002461 and PMID: 21914562), and one maternity confirmed de novo case via exome sequencing in PMID: 31683770 (PS2). PMID: 20002461 Western Blot studies showed reduced E1a, and Imbard et al 2011 PDC studies indicate activity <3rd percentile in fibroblasts (PP4). In silico predictors suggest a deleterious effect (REVEL score – 0.946; PP3). In summary, this variant meets criteria to be classified as a pathogenic of PDHA1- related pyruvate dehydrogenase deficiency in an X-linked manner. PDHA1-specific ACMG/AMP criteria applied: (PM1, PM2, PS2, PP3, PP4). This was reviewed with the PDHA1 expert panel on 4/6/2021 and approved on 4/6/2021.