BASEMENT-MEMBRANE ABNORMALITY IN MEROSIN-NEGATIVE CONGENITAL MUSCULAR-DYSTROPHY

In muscle biopsy specimens from three patients with merosin-negative c ongenital muscular dystrophy (CMD), there was marked variation in fibe r size with evidence of necrotic and regenerating processes and with m arked interstitial fibrosis. No muscle fibers or intramuscular nerves stained with merosin antibody, On electron microscopy, the basement me mbrane of all the muscle fibers was very poorly discernible and there were occasional disruptions, while the basement membrane of the Schwan n cells was well preserved. On the other hand, the sarcolemmal basemen t membrane in merosin-positive CMD was well preserved even in a patien t with severe interstitial fibrosis. It remains to be determined how t he defective basement membrane in merosin-negative CMD induces defecti ve sarcolemma and eventual fiber necrosis.