Combined oxidative phosphorylation deficiency type 3 is an extremely rare clinically heterogenous disorder described in about 5 patients to date. Clinical signs included hypotonia, lactic acidosis, and hepatic insufficiency, with progressive encephalomyopathy or hypertrophic cardiomyopathy. The disease is MONDO_0012512 (fatal mitochondrial disease due to combined oxidative phosphorylation defect type 3). Also known as: TSFM combined oxidative phosphorylation deficiency, combined oxidative phosphorylation deficiency caused by mutation in TSFM, combined oxidative phosphorylation deficiency type 3, fatal mitochondrial disease due to COXPD3.