Myoclonus epilepsy associated with ragged-red fibres (mitochondrial abnormalities): Disease entity or a syndrome?: Light- and electron-microscopic studies of two cases and review of literature

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Abstract

A report is given of an association of dyssynergia cerebellaris myoclonica associated with Friedreich's ataxia and mitochondrial myopathy in 2 patients. They had suffered from gradually increasing bursts of myoclonus since the age of 14 and childhood, respectively. The other striking clinical features included generalized convulsions, mental deterioration, intention tremor, ataxia, muscular atrophy and deformity of feet. Muscle biopsies revealed ragged-red fibres in both cases. On electron microscopy these fibres contained subsarcolemmal aggregations of abundant abnormal mitochondria with proliferation of inner membranes or paracrystalline inclusions. One of these patients showed elevated blood lactate and pyruvate with an increased lactate/pyruvate ratio, apparently of primary origin. These 2 cases resemble those reported briefly by Tsairis et al. (1974). An association of dyssynergia cerebellaris myoclonica associated with Friedreich's ataxia and mitochondrial myopathy in these 2 patients is unlikely to be coincidental but may represent one nosological entity. This myoclonus epilepsy syndrome associated with ragged-red fibres is compared with other possibly related mitochondrial encephalomyopathies.

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    This work was supported by a grant from the Ministry of Health and Welfare, Japan.

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