Clinical and pathological characteristics of pure type mitochondrial myopathy / 临床神经病学杂志

ABSTRACT

Objective To investigate the clinical and pathological features of pure type mitochondrial myopathy.Methods Clinical manifestations and pathological features of biopsied muscle specimens were summarized retrospectively in 9 cases of pure mitochondrial myopathy. 6 of them were followed up on the purpose of prognostic analysis.Results 9 cases of pure mitochondrial myopathy were clinical characterized by exclusive skeletal muscle involvement and fluctuating proximal muscle weakness. Extraocular muscles were spare. Most patients had moderately increased creatine phosphokinase level (539～2 913U/L). Electromyography examination showed myogenic changes in 6 cases and neurogenic in 3 cases. Pathologically, 8 cases had typical ragged red fibers (RRF) accounting for 5% to 60%. Mitochondrial intracristal inclusion bodies were observed by electron microscope in the patient with atypical RRF. Focal cytochrome C oxidase (COX) deficiency was seen in 4 cases and total deficiency in 2 cases. To a certain degree, the percentage of RRF was parallel to muscle weakness. Following-up data from 6 patients showed that symptoms had improved in 5 patients after treatment with vitamin B, vitamin E, CoQ 10 and inosine. One had a sudden death with unknown reason.Conclusion Pure mitochondrial myopathy may be a distinct subset of mitochondrial diseases that preferentially affects trunk and proximal muscles,Pathological charactoristic had typical RRF and COX deficiency,and RRF is related to patient's condition.It has relative chronic process and benign prognosis.