[Mitochondrial myopathy and mitochondrial encephalomyopathy]

To investigate the symptomatic, biochemical, and pathological characteristics of mitochondrial myopathy and mitochondrial encephalomyopathy.

Physical examination, electromyography, electroencephalography, cranial CT or MRI, serum enzymological examination, and light microscopy and electron microscopy of muscle biopsy specimens were made among twenty-one in-patients with the diagnosis of mitochondrial myopathy and mitochondrial encephalopathy. All the patients were followed up for more than 5 years.

Four patients died of lung infection, epilepticism or multiple organ failure 3, 4, 6, and 8 years after the onset of disease. One patient had already survived for 12 years. Among the 6 patients with the original diagnosis of mitochondrial myopathy, the diagnosis of two was changed as myoclonus epilepsy with ragged fiber (MERRF) 5 and 6 years after the onset. Among the seven patients whose disease was originally diagnosed as chronic progressive external ophthalmoplegia the diagnosis was changed as mitochondrial encephalomyopathy with lactic acidemia and stroke like episodes seven years after the onset.

It is not difficult to diagnose mitochondrial myopathy and mitochondrial encephalomyopathy based on the symptomatical, biochemical, and pathological characteristics. However, the clinical manifestations of these diseases may change during the progress of the disease. Follow-up is highly recommended.