A new mitochondrial DNA mutation associated with progressive dementia and chorea: a clinical, pathological, and molecular genetic study.

A novel mitochondrial DNA transfer RNA mutation at position 5549 was identified in a patient with dementia, chorea, cerebellar ataxia, deafness, and peripheral neuropathy in the absence of clinical myopathy. Muscle biopsy specimens showed ragged red and cytochrome oxidase-negative fibers, and reduced complex I activity on polarography. There was diffuse neuronal loss and gliosis throughout the brain on postmortem examination. The heteroplasmic mutation had a widespread distribution in autopsy tissues.