The m.13045A>C (p.M237L) variant in MT-ND5 has been reported in one individual with primary mitochondrial disease to date (PMID: 12509858), in a boy with migraine-like symptoms (dizziness, vomiting, photophobia), clonic seizures that developed into epilepsia partialis continua, bilateral optic atrophy, ophthalmoplegia, ataxia, and cognitive impairment. He also had elevated cerebrospinal fluid lactate (normal lactate in blood) and muscle biopsy showed mildly reduced complex I activity. His brain imaging findings were consistent with Leigh syndrome and mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS). The variant was present at 82% heteroplasmy in muscle and 13% in blood. The variant was absent in blood from his healthy mother (PM6_supporting). There are several occurrences in population databases (absent in gnomAD v3.1.2 and the Helix dataset; present in one individual in the MITOMAP GenBank sequences, 1/61168, 0.00163%). Although there are several occurrences, the frequency is still low (PM2_supporting). The computational predictor APOGEE gives a consensus rating of pathogenic with a score of 0.73 (Min=0, Max=1; score of 0.905 in APOGEE2), which predicts a damaging effect on gene function (PP3). There are no cybrids, supporting single fiber studies, or de novo occurrences reported for this variant. 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 November 13, 2023. Mitochondrial DNA-specific ACMG/AMP criteria applied (PMID: 32906214): PM2_supporting, PM6_supporting, PP3.