Genotype-phenotype associations for ARXgene duplication in X-linked mental retardation

We screened 165 mentally retarded patients for ARXgene 428-451 base pair (bp) duplication. Eighteen individuals from five families were found to carry the duplication, and all had intellectual impairment. Twelve presented with focal hand dystonia, while six patients had EEG abnormalities including seizures. Other symptoms included speech difficulties (4/18), testis enlargement (4/18), lower limb spasticity or foot dystonia (4/18), and facial telangiectasia (3/18). These features confirm the pleiotropic effect of the duplication.