An electron microscopical study of the T‐system in biopsied muscles from fukuyama type congenital muscular dystrophy

The behavior of the tubular system in muscles from six patients with Fukuyama type congenital muscular dystrophy (FCMD) was examined by electron microscopy using a lanthanum nitrate stain for a comparison with that in Duchenne muscular dystrophy (DMD). In FCMD, many fibers showed morphological changes of the T-system as follows: aggregated tubular components forming honeycomb-like structures, focal dilatation of T-tubules with tangle formation, and numerous longitudinally projecting tubules, which were quite similar to those found in cases with DMD. The fibers with abnormal T-systems occasionally showed ultrastructural characteristics of regenerating fibers, including excessive ribosome particles, immaturely organized myofibrils, and an increased number of internal nuclei and satellite cells. The present results suggested that there was no qualitative difference in the behavior of the T-system between FCMD and DMD, and the morphological changes of the T-system in dystrophic muscles were not primary lesions initiating myonecrosis but reflected the behavior of sarcotubular formation in the process of muscle regeneration.