The 22q11.2 microduplication syndrome is caused by non-allelic homologous recombination mediated by misalignments of low copy repeats located in the region deleted in the DiGeorge syndrome (DGS)/ velocardiofacial syndrome (VCFS). The variable phenotype of such condition, consisting in a combination of dysmorphic facial features, cognitive deficits, velopharyngeal insufficiency, congenital heart defects and immunologic derangement, is caused usually in 90% of cases by a 3 Mb deletion or in a minority of cases (7%) by a 1.5 Mb deletion. The most common reciprocal event of deletion is the 3 Mb duplication, reported more recently with a variable phenotype, ranging from multiple defects to normality. In this study, we report a 2.5-year-old girl with cognitive deficits and dysmorphic facial features such as superior placement of eyebrows, upslanting palpebral fissures, widely spaced eyes, broad nasal bridge and epicanthal folds. Fluorescent in situ hybridization for DGS/VCFS region on metaphase chromosomes did not show any apparent anomaly. Subsequent array comparative genomic hybridization study, confirmed by multiplex ligation-dependent probe assay and microsatellite analysis, disclosed a 1.5 Mb de novo 22q11.21 duplication concerning the same chromosomal region deleted in a minority of patients with DGS. These findings identify the minimal duplicated region leading to this emerging syndrome.
- 22q11.2 microduplication
- DiGeorge/velocardiofacial syndrome
- Low copy repeats
- Mental retardation
- Non-allelic homologous recombination
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