Duplication of the Williams-Beuren critical region: case report and further delineation of the phenotypic spectrum.

Only 12 patients with a duplication of the Williams-Beuren critical region (WBCR) have been reported to date, with variable developmental, psychomotor and language delay, in the absence of marked dysmorphic features. In this paper we present a new WBCR microduplication case, which supports the wide variability displayed by this duplication in the phenotype. The WBCR microduplication may be associated with autistic spectrum disorder, but most reported cases do not show this behavioural disorder, or may even show a hypersociable personality, as with our patient. From the present case and a review of the 12 previously described, we conclude that the phenotype associated with duplication of WBCR can affect the same domains as WBCR deletion, but that they cluster near the polar ends of social relationship (autism-like v hypersociability), language (expressive language impairment v "cocktail party" speech), visuospatial (severe v normal), mental retardation (severe v mild) and dysmorphic (severe v mild) features.