A 37-year-old man developed choreic movements of the limbs over a few months. His medical history included bilateral visual loss detected at the age of 9 and worsening at age 20. Visual field testing showed a central scotoma. Fundus examination showed atrophy of the optic disks and narrowing of vessels. The diagnosis of Leber hereditary optic neuropathy (LHON) was considered. There was no family history of visual loss or movement disorders. Blood lactate:pyruvate ratio was moderately elevated. Skeletal muscle biopsy was normal. Magnetic resonance imaging showed bilateral hypointense lesions on T1-weighted sequences in the subthalamic nuclei and in the lateral part of the substantia nigra. Linear hyperlucencies in the pyramidal tract facing the lateral part of the ruber nuclei were also demonstrated on T2-weighted sequences. Nine LHON-associated mutations were ruled out by RFLP analysis. Treatment with 250 mg coenzyme Q10 per day and multiple vitamins was initiated. Gradual recovery in movement disorders occurred over 1 year. Lactate to pyruvate ratio normalized. No change of visual function was observed. On magnetic resonance imaging performed 3 years later, lesions of the subthalamic nuclei almost completely disappeared. We think the patient might have an unusual, genetically uncharacterized mitochondrial disorder, combining optic neuropathy and chorea.