The m.4160T>C (p.L285P) variant in MT-ND1 has been reported in three unrelated individuals to date (PMIDs: 2018041, 22258525, 35699829), however only one case was included in this curation (PMID: 35699829). This individual had Leber Hereditary Optic Neuropathy (LHON) and dystonia, and the variant was present at 80.2% in blood, 90.8% in urine, and 81.7% in buccal. This variant occurred de novo in this individual as it was absent in blood, buccal, and urine samples from his mother and sister (PM6_supporting, PMID: 35699829). One of the other reported families with this variant had LHON however they also had the m.14484T>C variant, one of the three most common variants associated with LHON (PMIDs: 2018041, 29249004), and therefore was not included in this curation. Another individual was reported to have developmental delay, vision involvement, peripheral nervous system involvement, and muscle involvement however the m.4160T>C variant was only present at 11% heteroplasmy (PMID: 22258525). Given the low heteroplasmy, this case was also excluded from this curation. The computational predictor APOGEE gives a consensus rating of pathogenic with a score of 0.89 (Min=0, Max=1), which predicts a damaging effect on gene function (PP3). There are single occurrences in population databases, however these are from reported affected individuals (PM2_supporting). Cybrid studies were performed however were not considered in this curation given the presence of other mitochondrial DNA variants (PMIDs: 35699829, 28455970). In summary, this variant meets criteria to be classified as uncertain significance for primary mitochondrial disease inherited in a mitochondrial manner. This classification was approved by the NICHD/NINDS U24 ClinGen Mitochondrial Disease Variant Curation Expert Panel on January 8, 2024. Mitochondrial DNA-specific ACMG/AMP criteria applied (PMID: 32906214): PM2_supporting, PP3, PM6_supporting.