Required for cytochrome c complex (COX) IV assembly and function Protects COX assembly from oxidation-induced degradation, COX being the terminal component of the mitochondrial respiratory chain

Mitochondrion inner membrane

Mitochondrial complex IV deficiency, nuclear type 17

An autosomal recessive mitochondrial disorder with highly variable clinical manifestations and severity. Clinical features vary from acute neurometabolic decompensation in late infancy to subtle neurological signs presenting in adolescence. Encephalopathic episodes are characterized by acute loss of developmental milestones including ability to walk or sit, loss of speech, episodes with somnolence and seizure, and pyramidal signs rapidly evolving into spastic tetraparesis. The clinical course subsequently tends to stabilize and in several subjects marked recovery of neurological milestones is observed over time. Brain imaging shows a cavitating leukodystrophy, predominantly involving the posterior cerebral white matter and the corpus callosum in the acute stage, after which the abnormalities partially improve and then stabilize. Patient tissues show variably decreased levels and activity of mitochondrial respiratory complex IV.