Walsh & Hoyt: Diagnosis of Mitochondrial Myopathy in Patients with Ophthalmoplegia

It is important to distinguish the mitochondrial myopathies from autosomal-dominant oculopharyngeal muscular dystrophy and myasthenia gravis, because these disorders have distinct therapeutic and genetic implications. Muscle biopsy is the single most useful diagnostic tool for evaluating patients with suspected mitochondrial disease. The presence of RRFs on muscle biopsy, in excess of what can be accounted for by age, establishes the diagnosis of mitochondrial myopathy.