COA8 and hyperinsulinemic hypoglycemia, familial, 4: Loss of function mutations in APOPT1/COA8 (hereafter COA8) encoding cytochrome c oxidase assembly factor 8 have been associated with cavitating leukoencephalopathy with COX deficiency in 7 reported individuals.2,3 The disease was characterized by onset in childhood or adolescence of a leukoencephalopathy with cystic lesions predominantly in the posterior part of the cerebrum and sparing of the infratentorial parts of the brain.