The disease is Downs syndrome (trisomy 21). In addition to mental retardation and the characteristic physical findings described in the question stem, duodenal atresia is fairly common, as evidenced by the "double bubble" sign (gas in the stomach and duodenal bulb) on x-ray. These children are also likely to have various cardiac anomalies; endocardial cushion defect is the most common.Note:Atrial septal defect is one of the most common genetic defects in the general population, but is less common than endocardial cushion defect in patients with Down syndrome.Berry aneurysms, also known as saccular aneurysms, are typically located in the circle of Willis on the ventral surface of the brain. They occur more frequently in patients with adult polycystic disease. Rupture can produce subarachnoid hemorrhage.Coarctation of the aoa occurs more commonly in females with a 45, XO genotype (Turner syndrome). Ref: Brown D.W., Fulton D.R. (2011). Chapter 83. Congenital Hea Disease in Children and Adolescents. In V. Fuster, R.A. Walsh, R.A. Harrington (Eds), Hurst's The Hea, 13e.