The m.14459G>A (p.A72V) variant in MT-ND6 was reviewed by the Mitochondrial Disease Nuclear and Mitochondrial Variant Curation Expert Panel as part of the variant pilot for mitochondrial DNA variant specifications (McCormick et al., 2020; PMID: 32906214). This variant has been reported in >16 individuals with primary mitochondrial disease with variable features ranging from Leber Hereditary Optic Neuropathy (LHON) with or without dystonia, Leigh syndrome, bilateral basal ganglia lesions, ataxia, and migraines (PS4; PMIDs: 8016139, 7654063, 16380132, 10894222, 14735584, 21749722, 14735585, 28503604, 32045392, 29408632, 22426787). This variant has been identified as a de novo occurrence in at least 2 probands with primary mitochondrial disease (PM6; PMIDs: 14735584, 10894222). This variant heteroplasmy level segregated with severity in six family members from four families (PP1_moderate; PMIDs: 22426787, 21749722, 7654063, 8016139). The computational predictor APOGEE gives a consensus rating of pathogenic with a score of 0.93 (Min=0, Max=1), which predicts a damaging effect on gene function (PP3). Cybrid studies supported the functional impact of this variant including a deficiency seen in patient cell line that was transferred to cybrids with a high mutant load and study was reproducible (PS3_supporting; PMID: 8622678). In summary, this variant meets criteria to be classified as pathogenic for primary mitochondrial disease inherited in a mitochondrial manner. This classification was approved by the NICHD U24 ClinGen Mitochondrial Disease Variant Curation Expert Panel as of August 20, 2020. Mitochondrial DNA-specific ACMG/AMP criteria applied: PS4, PM6, PP1_moderate, PP3, PS3_supporting.