Follow-up study of a myopathy with loosely coupled mitochondria.

This communication deals with a clinical, histological, histochemical and biochemical follow-up study of a boy with an ameliorating myopathy with loosely coupled mitochondria who was studied earlier. In the course of about 15 years the clinical condition of the patient improved greatly. In a biopsy of skeletal muscle the same pathological features were found as before, but the pathological changes were much less severe. In contrast to earlier findings, the majority of the fibres with a loosely coupled state of the mitochondria belonged to the anaerobic type II fibres.