[Hypothyroid myopathy: a case report].

Though proximal muscle weakness is characteristic of polymyositis, other agents may also lead to proximal muscle weakness, such as drugs, endocrine diseases, or infections. Here, we report a thirty year-old female suffering from proximal weakness which initially was thought to be a case of polymyositis with high serum creatine phosphokinase level. Very low thyroid hormone levels were found as the history inquiry revealed constipation, hoarseness and cold intolerance. The muscle biopsy showed no obvious inflammation. After thyroxine therapy, her muscle weakness recovered. Up to now, hypothyroid myopathy with muscle mitochondrial abnormalities shown by electron microscopic examination has not been reported in the medical literature in Taiwan. Hypothyroid myopathy, though it is rare, may be misdiagnosed as polymyositis clinically. Therefore, it is recommended that hypothyroid myopathy should be considered in the differential diagnosis of proximal muscle weakness.