Physical examination of a neonate is remarkable for a holosystolic murmur. There is no cyanosis.Echocardiography demonstrates an ostium primum defect in the lower pa of the interatrial septum that is accompanied by malformations of the adjacent atrioventricular valves. These lesions are most likely associated with which of the following disorders?

The most common type of atrial septal defect is the ostium secundum type. Children with Down syndrome, however, are frequently afflicted with the ostium primum type of atrial septal defects, which may be accompanied by tricuspid and mitral valve malformations. More complex atrioventricular septal defects may also occur in this disorder. Children exhibiting these lesions should be specifically evaluated for chromosomal abnormalities. Clinically, the lesions produce left-to-right shunts with late cyanosis (after the right ventricle hyperophies in response to developing lung disease from the increased blood flow in the pulmonary system). Neither cystic fibrosis nor Gaucher disease is specifically associated with cardiovascular defects. Dissecting aoic aneurysm is associated with Marfan syndrome . Ref: Tsaic A.C., Manchester D.K., Elias E.R. (2012). Chapter 37. Genetics & Dysmorphology. In W.W. Hay, Jr., M.J. Levin, R.R. Deterding, J.J. Ross, J.M. Sondheimer (Eds), CURRENT Diagnosis & Treatment: Pediatrics, 21e.