ISOLATED MITOCHONDRIAL MYOPATHY MISDIAGNOSED AS POLYMYOSITIS

Mitochondrial myopathies are caused by dysfunction of the mitochondria and are systemic disorders that present with diverse clinical manifestations. They have been found to be especially prevalent in children. In this report, we present the case of a 55-year-old male patient who developed progressive symmetric proximal muscle weakness in both upper and lower extremities. Although the elevated levels of muscle enzymes and the findings of magnetic resonance imaging of lower extremities were suggestive of polymyositis, we made a final diagnosis of isolated mitochondrial myopathy based on the result of the biopsy of the thigh muscle. In this report, we emphasize the importance of performing a correct differential diagnosis of myopathies, particularly in the cases without evidence of involvement of other organs.