Microduplication of Xp11.23p11.3 with effects on cognition, behavior, and craniofacial development.

We report an ~1.3 Mb tandem duplication at Xp11.23p11.3 in an 11-year-old boy with pleasant personality, hyperactivity, learning and visual-spatial difficulties, relative microcephaly, long face, stellate iris pattern, and periorbital fullness. This clinical presentation is milder and distinct from that of patients with partially overlapping Xp11.22p11.23 duplications which have been described in males and females with intellectual disability, language delay, autistic behaviors, and seizures. The duplicated region harbors three known X-linked mental retardation genes: FTSJ1, ZNF81, and SYN1. Quantitative polymerase chain reaction from whole blood total RNA showed increased expression of three genes located in the duplicated region: EBP, WDR13, and ZNF81. Thus, over-expression of genes in the interval may contribute to the observed phenotype. Many of the features seen in this patient are present in individuals with Williams-Beuren syndrome (WBS). Interestingly, the SYN1 gene within the duplicated interval, as well as the STX1A gene, within the WBS critical region, co-localize to presynaptic active zones, and play important roles in neurotransmitter release.