Background: Microdeletions at 17q21.31 have recently been shown to cause a novel syndrome. Here we identify the reciprocal 17q21.31 duplication syndrome in 4 patients.
Method: Patients with the 17q21.31 duplication were identified by screening a large cohort of patients (n = 13 070) with mental retardation and congenital malformation by comparative genomic hybridisation microarray. Parental origin was investigated in 3 patients by quantitative polymerase chain reaction and microsatellite genotyping.
Results: In three cases it was possible to show that duplication arose de novo. Intellectual skills range from normal to mild mental retardation. Patients are characterised by poor social interaction, with relationship difficulties, reminiscent of autistic spectrum disorders. Other features are rather variable with no striking common phenotypic features. Parental origin was investigated for 3 patients. In all cases duplication was of maternal origin either through interchromosomal (2 cases) or interchromatid (1 case) rearrangement. The 3 mothers are all carriers of the inverted H2 haplotype, emphasising the role of local genomic architecture alteration as a predisposing factor for this duplication.
Conclusion: Autistic features observed in our patients suggest that genes in the duplicated interval should be considered as candidates for disorders in the autistic spectrum. Other phenotypic observations are rather variable or aspecific. This adds 17q21.31 duplications to a growing group of recently identified genomic disorders with variable penetrance and expressivity.
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▸ Additional tables and figures are published online only at http://jmg.bmj.com/content/vol46/issue8
Funding: This work was funded by a grant from the Institute de Recherche Scientifique en Pathologie et en Génétique and by grants to JV from the Catholic University of Leuven (GOA/2006/12 and Centre of Excellence SymBioSys, Research Council K.U.Leuven EF/05/007) and the IWT (IWT 60848). This work was also funded by a Biomedical Research grant from the National Institute for Health Research (NIHR), UK.
Competing interests: J Rosenfeld is an employee of Signature Genomic.
Patient consent: Obtained.
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