The Williams–Beuren critical region (WBCR), located in 7q11.23, is commonly deleted in Williams–Beuren syndrome (WBS), a microdeletion syndrome. However, only 12 patients with a duplication of the WBCR have been reported to date, with variable developmental, psychomotor and language delay, in the absence of marked dysmorphic features. In addition, this duplication has been found to be inherited from healthy parents in three cases.

In a recently published paper, Depienne et al1 included for the first time autistic spectrum disorder among the features associated with WBCR microduplication syndrome. More recently, a paper describing seven new cases with this alteration also reported autistic behaviour in two of them.2

In this paper we present a new WBCR microduplication case, which supports the wide variability displayed by this duplication in the phenotype. More specifically, the WBCR microduplication may be associated with autistic spectrum disorder, but most reported cases do not show this behavioral disorder, or may even show a hypersociable personality, as with our patient. From the present case and a review of the 12 previously described,1^–6 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. They do not present a clear profile like that resulting from WBCR deletion.

This male patient was initially referred at the age of 13 years with polymalformation syndrome and mental retardation. A karyotype performed at the 400–500-band level was normal, and molecular analysis for 22q11 deletion and the fragile X syndrome was negative.

The patient is the first child of consanguineous (second-degree cousins), healthy parents. A maternal …