CPEO, MERRF and Melas

Mitochondrial Encephalomyopathies are a group of disorders with mitochondrial dysfunction affecting the central nervous system and skeletal muscle. These disorders also involve other systems such as retina, heart and peripheral nerve. They include disorders of infancy or early childhood, such as Alper's disease, Canavan's disease, Menke's disease and Leigh'sdiseaseasweli asagroup of disorders with apparently normal earlydevelopment followed by a progressive neurologic disorder. The latter group includes a myriad of case reports, each with its own clinical constellation. Within this group there are three relatively distinctive syndromes, chronic progressive external ophthalmoplegia (CPEO), including the Kearns-Sayre syndrome (KSS), mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS) and myoclonic epilepsy with ragged red fibers (MERRF). Abnormalities in mitochrondrial DNA (mtDNA) have recently been demonstrated for these three diseases.