A type of mitochondrial disease charcterized by macrocephaly (large head) with progressive leukodystrophy, encephalopathy, hypertrophic cardiomyopathy, myopathy, liver disease, Leigh syndrome, Leber hereditary optic neuropathy, and some forms of Parkinson disease. The disease is caused by mutations in any of many genes and the inheritance pattern depends on the responsible gene. The disease is mitochondrial complex I deficiency (MONDO_0100133). Also known as: NADH coenzyme Q reductase deficiency, complex 1 mitochondrial respiratory chain deficiency, isolated NADH-CoQ reductase deficiency, isolated NADH-coenzyme Q reductase deficiency, isolated NADH-ubiquinone reductase deficiency, isolated complex I deficiency, isolated mitochondrial respiratory chain complex I deficiency, mitochondrial respiratory chain complex I deficiency.