CONGENITAL MUSCULAR-DYSTROPHY WITH MEROSI N DEFICIENCY - CLINICAL, HISTOPATHOLOGICAL, IMMUNOCYTOCHEMICAL AND GENETIC-STUDY

A selective deficiency of a specific laminin isovariant, merosin made of M, B-1 and B-2 chains, was found in a series of 17 patients affecte d with congenital muscular dystrophy (CMD). The merosin deficiency was complete in 15 cases, and almost complete in two cases. An overexpres sion of the laminin A chain was seen in these biopsies, while B-1 and B-2 chains were normally expressed. Comparison of the clinical data wi th a series of 18 <<merosin-non deficient>> cases showed that the <<me rosin-deficient>> cases were forming a more homogenous group than the <<non-deficient>> one. Hypotonia, contractures, motor development dela y were generally more severe in the <<merosin-deficient>> series of ca ses. Moreover white matter alterations were seen in most cases explore d by MRI or scan imaging. A genetic linkage with a 6q2 locus, correspo nding to the M chain gene localization, was found in a panel of inform ative families from French and Turkish origin with <<merosin deficient >> CMD. <<Merosin non-deficient>> families did not map on this locus. So, the <<merosin-deficient>> CMD can be considered as a peculiar enti ty within the group of Congenital Muscular Dystrophies.