Mitochondrial disorders and ataxia.

Mitochondrial disorders are important causes of progressive ataxia in children. Clinical examination, metabolic studies, imaging studies, muscle biopsies, and mitochondrial DNA studies are required to arrive at a specific diagnosis. There is poor correlation between phenotype and genotype in mitochondrial disorders. Ataxia is a major clinical presentation in Kearns-Sayre syndrome; mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes; myoclonic epilepsy with ragged-red fibers; neurogenic muscle weakness, ataxia, and retinitis pigmentosa; Leigh's syndrome; and coenzyme Q10 deficiency.