A young adult has progressive intellectual deterioration, weakness, ataxia, and seizures. Reference laboratory tests demonstrate an abnormality of an impoant mitochondrial enzyme. From which of the following diseases is this person most likely suffering?

Leigh's disease, also known as subacute necrotizing encephalomyelopathy, is a very rare disease. The specific defective enzyme, in at least some cases, is cytochrome oxidase, one of the components of the electron transpo system. Muscle and brain are paicularly affected. Patients have the presentation described in the question and typically die within several years. Adrenoleukodystrophy is an X-linked disease with abnormal lipid metabolism leading to demyelination in the CNS. Central pontine myelinolysis is characterized by demyelination of the pons (especially the basis pontis) seen after overlying rapid correction of hyponatremia. Krabbe's disease is an autosomal recessive accumulation of cerebrosides in histiocytes in the CNS. Ref: Ropper A.H., Samuels M.A. (2009). Chapter 37. Inherited Metabolic Diseases of the Nervous System. In A.H. Ropper, M.A. Samuels (Eds), Adams and Victor's Principles of Neurology, 9e.