ABORDAGEM DIAGNÓSTICA DA SÍNDROME DE WILLIAMS - BEUREN.

Abstract

Chromosomal abnormalities cause specific and complex phenotypes due to imbalance in the normal dosage of genes located in a specific chromosomal segment. They account for 60% or even more of all the identifiable genetic syndromes. Williams-Beuren syndrome (WBS) is related to a group of multiple defects and intellectual disabilities, described independently by Williams et al. (1961) and Beuren et al. (1962). The WBS is a genetic disease characterized by a microdeletion of the 7q11.23 region, which delay the physical and intellectual development and it is associated with congenital cardiac abnormalities, facial dimorphism, mental retardation and occasionally infantile hypercalcemia.The existing phenotypic variation in this syndrome hinders clinical diagnosis.Through the development of new cytomolecular technologies and the increased number of studies regarding the clinical features of this syndrome, seeks a better understanding of the genotype-phenotype correlation in WBS. The present study reports some of these techniques used for the diagnosis of WBS, such as Karyotype, MLPA, PCR, with emphasis on FISH and CMA. Additionally, we described four patients who were referred to LaGene/SES and NPR/PUC by the public health service. Three of them had clinical suggestion of WBS and the fourth patient of ID. The confirmation was unsuccessful regarding the diagnostic through techniques of conventional cytogenetics for all of the patinets. FISH technique was useful in the diagnostic investigation of a patient while CMA was used to study the other 3 cases. Chromosomal microarray analysis detected long stretches of homozygosity of uncertain clinical significance at the Xq11.1q13.1 region and a microduplication at the 7q11.23 region, the latter is defined as a critical region of WBS. The study of genotype-phenotype correlation in WBS has been established for some genes detected by CMA. But other genes did not show a strong relation to the syndrome, thus requiring further investigation.