Médecine moléculaire et génétique

Cytogenetic Profiles of 1213 Children with Down Syndrome in South Region of Turkey

Abstract

Osman Demirhan, Nilgun Tanriverdi, Dilara Suleymanova and Nesrin Cetinel

Down syndrome (DS) is a complex disorder characterized by well-defined and distinctive phenotypic features. Different karyotypes are associated with varying phenotypic expression of DS. The type of karyotypes in the children with DS plays an important role in genetic diagnosis and family counselling. This study describes the characteristics of karyotypes leading to phenotypic Down syndrome in 1213 cases diagnosed between 1992 and 2009 in South Region of Turkey. The frequency of occurrence of the different karyotypes was analyzed. The karyotype results were normal in 9.1% of all cases. However, chromosomal abnormalities (CAs) were detected in nearly 91% of all cases. The free trisomy 21 was the most common karyotype (nearly 93% of all cases). The ration of mosaic trisomy 21 was 2.5%. The CAs in addition to trisomy 21 was present in 1.5% of cases. The ratio of Robertsonian and reciprocal translocations in these variants were 2.3% and 0.3%, respectively. The ration of other variants was nearly 1%. This study showing the frequency and distribution of karyotypes causing DS, are the great value to be gleaned from studies of DS patients in furthering our understanding of the atypical clinical features associated with DS. These cytogenetic investigations carried out greatly helped in the management of these children and for counseling the affected families.