Trisomy 18

Diagnosis

The clinical findings include low birth weight, hypertonia and characteristic facial features with microcephaly, dolichocephaly, prominent occiput, narrow palpebral fissures, hypoplasia of the malar areas, a small mouth, retrognathia, low set malformed ears. Brain abnormalities include hypoplasia or absence of the corpus callosum, Dandy-Walker malformation, absent septum pellucidum, periventricular heterotopia, short frontal lobe and abnormal gyri. The neck manifestations are redundant nuchal skin and thyroglossal cyst. The chest has a short sternum, widely spaced and hypoplastic nipples and eventration/hernia of the diaphragm. Cardiac abnormalities are common and include polyvalvular abnormalities, VSD, PDA, hypoplastic left heart, coarctation of the aorta, PDA and PFO. The abdomen shows inguinal and umbilical hernia, single umbilical artery. Gastrointestinal abnormalities include esophageal atresia, ectopic pancreas and anal atresia. Renal abnormalities including cystic kidneys, hypoplastic kidneys, and horseshoe kidneys and double ureters are common. Genital abnormalities include cryptorchidism, prominent clitoris and hypoplasia of the labia majora, bicornuate uterus and ovarian cyst. The pelvis is small and the limbs shows overlapping fingers, hypoplastic nails, club foot, prominent calcaneus, rocker-bottom feet.