Leigh's disease in an adult with evidence of "inhibitor factor" in family members.

A 21-year-old man with a longstanding history of impaired visual acuity, strabismus, broad-based gait, and below-average intellectual capacity developed respiratory difficulties and intermittent generalized weakness at age 19. He subsequently showed signs of massive brainstem dysfunction and died. Postmortem examination demonstrated changes compatible with subacute necrotizing encephalomyelopathy of Leigh involving portions of the diencephalon, midbrain, pons, and medulla as well as portions of the spinal cord and optic nerves. Evaluation of family members for presence of the urinary inhibitor factor for thiamine diphosphate phosphoryl transferase revealed abnormal levels in a brother, a maternal uncle, and the maternal grandfather of the patient.