CONGENITAL MUSCULAR-DYSTROPHY WITH PARTIAL MEROSIN DEFICIENCY AND LATE-ONSET EPILEPSY

Merosin, the laminin alpha 2 chain located on the surface of muscle fi bers, has recently been shown to be absent in a subset of cases with t he classical type of congenital muscular dystrophy (C1-CMD). By immuno cytochemistry and immunoblot analysis, using monoclonal antibodies to both the 80- and the 320-kDa fragments, the same protein was found to be only partially deficient in 3 of our cases. All these 3 patients we re able to walk, with evidence of a mild to moderate muscle involvemen t, as opposed to the merosin-negative cases which are never ambulant b ecause they are affected by severe muscular deficit. All of them also suffered from a late onset form of epilepsy, a clinical expression of brain involvement rarely described in cases with merosin-negative CMD. The 3 patients with CMD and partial merosin deficiency were investiga ted by brain MRI and pattern reversal visual evoked potentials (VEP) a ssociated with electroretinography (ERG). The results were compared wi th those obtained by similar studies on 3 of our cases with complete m erosin deficiency. In both types of patients, the neuroimaging evaluat ion showed supratentorial white matter changes, usually of moderate de gree, irrespective of the amount of merosin detected in muscle. The VE P were normal in all the 3 cases with partial merosin deficiency, wher eas they showed reduced amplitude or prolonged latency in all the 3 ca ses with the merosin-negative form. ERG was normal in all 6 cases. As a whole, our data indicate that leukoencephalopathy does not seem to d istinguish between the two variants of Cl-CMD. On the other hand, a be nign muscle involvement and normal VEP findings seem to distinguish CM D patients with partial merosin deficiency from those with complete de ficiency of the same protein. Late onset epilepsy, evident in all our 3 cases with partial merosin deficiency, needs to be evaluated in a la rger series of patients in order to be considered a characteristic of this variant of CMD.