RESUMO
Mitochondrial myopathy is a group of multisytemic disease, variable in the age at onset, frequency, clinical data, evolution and prognosis. It results from nuclear or mitochondrial DNA mutation or from defective interaction between nuclear and mitochondrial DNA. The transmission of this mitochondrial myopathy is exlusively maternal. Sometimes the mutationns are born in the maternal ovule, or early in the embryonal life. The diagnosis is suspected on clinical manifestations and is confirmed by existence of ragged - red - fibers in the muscular biopsy, and especially, by molecular study which discovers the mutation of mitochondrial DNA. The treatment is often disappointing, however some specific measures are necessary to improve the quality of patients life