Movement disorders and mitochondrial dysfunction.

Primary defects of mitochondrial DNA leading to respiratory chain dysfunction have been described in association with dystonia, chorea and parkinsonism. Myoclonus remains the commonest movement disorder associated with such defects. The genetic basis of Leigh's syndrome, which is frequently associated with movement disorders, may be mitochondrial or nuclear. Respiratory chain dysfunction has been identified in Huntington's disease in addition to Parkinson's disease, but the cause and relationship of this dysfunction to the pathogenesis of these common disorders is not yet determined.