Previously reported pathogenic variants in MT-ND1 include m.3376G>A, p.(Glu24Lys) reported to cause a Leber hereditary optic neuropathy/mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) overlap syndrome and m.3697G>A,p.(Gly131Ser), associated with MELAS and Leigh syndromes. This evidence concerns the gene MT-ND1 and lactic acidosis.