Changes in the spectrum of organic acids are relatively non-specific and include high concentrations of the Krebs cycle metabolites: 2-hydroxyisobutyrate, 3-hydroxybutyrate, 2-oxoglutaric acid, lactate, pyruvate, fumarate, succinate, etc. In cases with PDHA1-associated LS, a high level of alanine in blood is frequently observed and for the m.8993T>C/G variant low citrulline in blood (2/10; 20%) was noted which was previously reported in the literature [21]. Here, PDHA1 is linked to Leigh syndrome.