Down Syndrome - Genetics and Cardiogenetics

Abstract

During the last years, Down syndrome has been the focus of special attention. Down syndrome is a genetic disorder characterized by distinct physical features and some degree of cognitive disability. Patients with Down syndrome also present many other congenital anomalies. The mapping for phenotypes to specific regions of chromosome 21 permits to identify which genes (or small regions) contribute to the phenotypic features of Down syndrome and thus, to understand its pathogenesis. Mainly there are three cytogenetic forms of Down syndrome: free trisomy 21, mosaic trisomy 21 and robertsonian translocation trisomy 21. Prenatal and postnatal testing has become commonly used to diagnose different cases presenting the same pathology. Early clinical diagnosis is extremely important for patient prognosis. Lately, advances in Down syndrome research have been registered, but little is known about cardiovascular phenotype in Down syndrome. About half of patients with Down syndrome have congenital heart disease, and atrioventricular septal defects are the most common defects found. Basic research on Down syndrome is now rapidly accelerating, using new genomic technologies. There were many studies performed to identify a correlation between genotype and phenotype in Down syndrome.

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Origins of Trisomy 21 (Gardner RJ, Sutherland G, Shaff er L, 2012)

FIGURE 1.

Normal karyotype: 46,XY (image by courtesy of genetic laboratory of Alessandrescu-Rusescu INSCM)

FIGURE 2.

A female newborn with Down syndrome with a karyotype showing a free trisomy 21: 47,XX,+21 (image by courtesy of genetic laboratory of Alessandrescu-Rusescu INSCM)

FIGURE 3.

A girl with Down syndrome with a karyotype showing a Robertsonian translocation 14;21: 46,XX,t(14;21)(q10;q10),+21 (image by courtesy of genetic laboratory of Alessandrescu-Rusescu INSCM)