DISRUPTION OF MUSCLE BASAL LAMINA IN CONGENITAL MUSCULAR-DYSTROPHY WITH MEROSIN DEFICIENCY

We studied three new cases of congenital muscular dystrophy (CMD) with homogeneous clinical and laboratory features, represented by congenit al muscle hypotonia and weakness, early contractures, elevated serum C K, and dystrophic pattern at muscle biopsy, without clinical impairmen t of CNS. Merosin, the laminin isoform that contains the alpha 2 heavy chain, was absent in muscle fibers of all the patients by immunohisto chemistry and by immunoblot. By electron microscopy, we found a severe disruption of muscle fiber basal lamina, but not of blood vessel basa l lamina, which contains the laminin alpha 1 heavy chain isoform. This disruption may play a key role in the degeneration of muscle fibers a nd in the abnormal proliferation of connective tissue seen in CMD.