Résumé :
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Congenital myopathies are inherited muscle diseases which most often manifest in early life and are distinguished by structural muscle biopsy abnormalities. We describe the morphology of a patient with a slowly progressive proximal myopathy with unique crystalloid inclusions in type 2 muscle fibres. The male patient presented at the age of 24 years with a mild muscle weakness and exercise intolerance. As first symptoms at the age of 20y, he had noticed fatigability and difficulty to keep up with peers in sports. He underwent two muscle biopsies in the deltoid muscle (24,35y), in which pathomorphology didn’t change. Some muscle fibres showed a large number of small inclusions, single or multiple, in their periphery or centre. The inclusions were strongly eosinophilic, and fuchsinophilic by the Gomori trichroom method. With oxidative reactions in enzymohistochemistry, the inclusions were almost invisible. They showed no activity in myofibrillar ATPase. The inclusions were selectively present in type 2 fibres. The inclusions were negative for the immunohistochemical reactions for vimentin, desmin, ubiquitin, alpha-actinin and the subtypes of myosin heavy chain. At the ultrastructural level, the inclusions were composed of vesicular profiles, approximately 20 nm in cross-diameter, connected by radially arranged bars. The architecture was highly regular, with a hexagonal pattern of distribution and spacing of circular profiles. The crystalloid inclusions showed an oval or trapezoid shape, and were arranged along the myofibrils in their longitudinal axis, where they displayed fine parallel dense lines. Within several of the hexagonal crystalloid structures, small areas containing glycogen granules could be observed. At these sites, the highly structured hexagonal pattern was interrupted. The inclusions were morphologically different from tubular aggregates and nemaline bodies. The inclusions were not related to any normal cellular organelle. We suggest that this is the fourth case of a new congenital myopathy with characteristic intracytoplasmic inclusions.
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