X-LINKED SEVERE MENTAL-RETARDATION AND A PROGRESSIVE NEUROLOGICAL DISORDER IN A BELGIAN FAMILY - CLINICAL AND GENETIC-STUDIES

The combination of X-linked mental retardation (XLMR) and neurological disorders occurs in a number of syndromes. Differential diagnosis mos tly depends on clinical data and mapping of responsible genes by linka ge analysis. We present a Belgian family with severe XLMR and a progre ssive neurological disorder with ataxia, spasticity and convulsions. B iochemical investigations, neuroimaging and neuropathology were normal . Linkage analysis pointed to region Xq27-28 as the probable locus for the genetic defect. The sequence of the L1CAM cDNA, a possible candid ate gene, proved to be normal in the patients. This suggests the prese nce of a genetic factor on Xq27-28, different from L1CAM, which can le ad to severe XLMR and a progressive neurological disorder.