[Electronoptical, morphometric and histochemical studies on skeletal muscles of patients with polymyalgia rheumatica]

1. Skeletal muscle biopsies from 21 patients with polymyalgia rheumatica (PMR) were examined morphometrically, histochemically, and by electron microscopy. 2. Ultrastructural changes in the PMR specimens have been classified according to 15 criteria including nucleus, myofilaments, mitochondria, T-system, glycogen deposition, lipid, lipofuscin and myelin figures. 3. The described focal muscle changes are of regressive character and nonspecific in themselves. 4. The described recording of these criteria shows an extraordinarily high incidence of skeletal muscle changes in PMR. This constellation of characteristics gives a distinctive profile to the ultrastructural picture of the skeletal musculature in PMR. 5. The most important ultrastructural changes concern the mitochondria. Crystalline inclusions and deformations lead to structural changes of the mitochondria which threaten the breathing of the cells. This, however, is compensated by the reproduction and accumulation of the mitochondria. 6. A similar analysis of the regressive muscle changes and the processes in the field of muscular artery media shows morphological analogies pointing to an identical systemic process in PMR and arteritis gigantocellularis. 7. Ultrastructural changes of this kind cannot be explained by inflammatory or noninflammatory arterial occlusions. The same applies to the light microscopic muscle findings. 8. Minor type II fiber atrophy and some moth-eaten and whorled fibers were demonstrated histochemically. These findings are not specific to PMR, being found in skeletal muscle diseases of varying origin.