Genotype-phenotype correlation and the size of microdeletion or microduplication of 7q11.23 region in patients with Williams-Beuren syndrome.

Williams-Beuren syndrome (WBS) is a chromosomal microdeletion syndrome with variable phenotypic features such as supravalvular aortic stenosis (SVAS), facial appearance characteristics, growth retardation, and infantile hypercalcemia. This study aimed to detect the 7q11.23 microdeletion in 10 patients with early clinical diagnosis of WBS using fluorescent in situ hybridization or array comparative genomic hybridization. As an alternative method, multiplex ligation-dependent probe amplification (MLPA) was used to confirm this microdeletion. Clinical features were also compared with detected genotypes. To reveal the parental origin of deletion, four polymorphic markers (D7S1870, D7S489, D7S613, and D7S2476) were used. The deletion had maternal origin in 80% and paternal origin in 20% of the cases. From 10 patients with early clinical diagnosis of the WBS, 3 patients presented with atypical phenotypes such as infantile hypocalcemia, normal IQ, and normal facial characterization, but the sizes of their deletions seemed to be almost similar to other cases. Regarding such observation, we suggest that the phenotypic variations of WBS are influenced not only by the deletion size and involving genes but also by the breakpoint regions and probably epigenetic effects. However, further research is required to explore the effect of such parameters on phenotypic features.