Orphanet_168566 (Fatal mitochondrial disease due to combined oxidative phosphorylation deficiency 3) can be described as follows. 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.