ABSTRACT
<p><b>OBJECTIVE</b>To explore the genetic cause for a child with mental retardation, developmental delay and multi-systemic developmental disorders by analyzing the copy number variations (CNVs) and correlating the genotype with the phenotype.</p><p><b>METHODS</b>Routine G-banding was performed to analyze the karyotype of the patient and her parents. In addition, single nucleotide polymorphisms array (SNP-array) was used to determine the CNVs, which was confirmed by fluorescence in situ hybridization (FISH).</p><p><b>RESULTS</b>No karyotypic abnormality was detected upon chromosome analysis. However, SNP-array has identified a de novo hemizygous deletion of 1673 kb on chromosome region 7q11.23, which has been associated with Williams-Beuren syndrome. The microdeletion was confirmed by FISH testing.</p><p><b>CONCLUSION</b>A child with Williams-Beuren syndrome has been diagnosed by SNP-array and FISH. The de novo 7q11.23 microdeletion probably underlies the clinical manifestation of the patient. Compared with routine karyotype analysis, SNP-array is more useful for diagnosing children with multiple congenital anomalies with unclear etiology.</p>