[Histochemical and ultrastructural study of myotonic dystrophy]

The pathological, histochemical and ultrastructural changes in the muscular biopsies from 9 patients with myotonic dystrophy were investigated. The major changes observed under light microscopy were degeneration of muscle fibers, increased number of nuclei, tendency of central nuclei to form chains, subsarcolemmal masses of cytoplasm and circularly arranged fibrils. The myosin ATPase and NADH-TR stain demonstrated histochemical selectivity of type I fiber atrophy in 7 of the 9 cases studied. The outstanding ultrastructural changes were extensive small disruptions of plasma membrane, destructions of Z bands and myofilaments, swelling of mitochondria, dilatational sarcoplasmic reticulum and regeneration of muscle fibers. Genetic fault of the surface membrane is a possible cause that leads to enzyme metabolic disorder, mitochondrial calcium overload, increased calcium content in sarcoplasm, resulting finally in mitochondrial metabolic disorder, myofilament destruction and muscle fiber necrosis.