CHROMOSOME 7q11.23 DUPLICATION SYNDROME

Chromosome 7q11.23 duplication syndrome (also known as Williams-Beuren region duplication syndrome, OMIM 609757) is a developmental disorder characterized by speech delay, craniofacial dysmorphisms and other malformations such as heart defects, diaphragmatic hernia and cryptorchidism. Although intelligence may be not affected, several patients show mental retardation or autism. First described by Somerville MJ et al (2005, PMID: 16236740), the syndrome arises from the duplication of the chromosomal region at 7q11.23. This region is somehow subject to frequent chromosomal rearrangements, including the microdeletion causing the phenotype of Williams-Beuren syndrome (WBS, characterized by developmental delay, supra valvular aortic stenosis and other congenital cardiopathies, facial dysmorphism and, interestingly, hypersocial behaviour with high noise sensitivity and good musical abilities). Of note, hypersensitivity to noise, typical of WBS, has been described also in Williams-Beuren region duplication syndrome (PMID: 17400790). Evidences of clinical variability or incomplete penetrance have been reported by Berg et al. (2007) and Torniero et al (2008), who found the same duplication to be carried also by unaffected or mildly affected parents (PMIDs: 17666889 and 18337728). Very interestingly, Beunders et al. (2010) reported a case of triplication of the WBS critical region, whose clinical presentation appeared to be similar but more severe than what is usually found in patients with the duplication (PMID: 19752158). References: see text.