This study deals with a case of "ophtalmoplegia plus" with histochemistry and electron microscopy of a muscle biopsy and full pathological examination in a 29 year old woman. Ragged-red fibers with abnormal mitochondria, cerebral spongiosis mostly involving white matter, perimacular pigmentary retinopathy and scattered myocardial fibrosis interrupting the Hiss'bundle were found. A goiter with hypersecretion of thyroid hormones and thyroid and ocular muscles changes characteristics of Graves' disease without any hypermetabolism occurred in her late twenties. This could be related to the absence of response from the abnormal mitochondria to the thyroid hormones.