Deficiency of merosin (laminin M or alpha 2) in congenital muscular dystrophy associated with cerebral white matter alterations

Recently, a deficiency of merosin has been reported in patients with classical congenital muscular dystrophy (CMD), while other patients, with indistinguishable clinico-pathological features, do not present this deficiency, suggesting genetic heterogeneity. The purpose of the present investigation was to assess merosin distribution and quantity in 21 clinically well characterized Brazilian CMD patients, in order to: a) estimate the proportion of merosin-deficient cases in this group of patients; b) characterize phenotypically merosin-negative, as compared to merosin-positive patients. Merosin deficiency was found in 11 patients and all the seven who had been submitted to neuroimaging studies showed evidence of periventricular dysmyelination. A normal pattern of 43 DAG was found in all patients, which suggest that this protein is not preferentially involved in a third form of merosin-positive CMD. Results from the present study are further suggestive, but do not prove, that the association of merosin deficiency with white matter alterations represents a genetic entity with common clinical, laboratory and neuroimaging findings.