Clinical features

• face: upslanting palpebral fissures, epicanthic folds, Brushfield spots in iris, protruding tongue, small low-set ears, round/flat face
• flat occiput
• single palmar crease, pronounced 'sandal gap' between big and first toe
• hypotonia
• congenital heart defects (40-50%, see below)
• duodenal atresia
• Hirschsprung's disease

Cardiac complications

• multiple cardiac problems may be present
• endocardial cushion defect (most common, 40%, also known as atrioventricular septal canal defects)
• ventricular septal defect (c. 30%)
• secundum atrial septal defect (c. 10%)
• tetralogy of Fallot (c. 5%)
• isolated patent ductus arteriosus (c. 5%)

Later complications

• subfertility: males are almost always infertile due to impaired spermatogenesis. Females are usually subfertile, and have an increased incidence of problems with pregnancy and labour
• learning difficulties
• short stature
• repeated respiratory infections (+hearing impairment from glue ear)