RESUMEN
Five cases of sirenomelia presented with rare manifestations are discussed. Three neonates were born alive and died within 2 to 12 hours after birth. One case was the offspring of a triple in vitro fertilization pregnancy with history of early intrauterine death of one of the triplets. The main features included fusion of lower extremities (five of five), renal agenesis (three of five), polycystic renal dysplasia (two of five), anal atresia with large bowel hypoplasia (three of five), pulmonary hypoplasia (four of five), and single umbilical artery (five of five). Other features that have only rarely been associated with sirenomelia included concurrence of congenital heart disease and neuroblastoma, gallbladder agenesis, and upper extremity defects.