An incomplete closure of the abdominal wall.

Gastroschisis is a congenital defect of the abdominal wall that occurs laterally to, and often to the right of, a normally closed umbilical ring. Visceral organs that herniate through the defect are not covered by a membrane. Gastroschisis is distinct from omphalocele (164750), which is characterized by herniation of abdominal contents through the base of the umbilical cord; in omphalocele, the visceral organs are covered by membranes (summary by Mastroiacovo et al., 2007). Both omphalocele and gastroschisis, when they occur without other malformations, are probably multifactorial (Baird and MacDonald, 1981).

Constriction rings syndrome is a congenital limb malformation disorder with an extremely variable clinical presentation characterized by the presence of partial to complete, congenital, fibrous, circumferential, constriction bands/rings on any part of the body, although a particular predilection for the upper or lower extremities is seen. Phenotypes range from only a mild skin indentation to complete amputation of parts of the fetus (e.g. digits, distal limb). Compression from the rings may lead to edema, skeletal anomalies (e.g. fractures, foot deformities) and, infrequently, neural compromise.

Nager syndrome is the prototype for a group of disorders collectively referred to as the acrofacial dysostoses (AFDs), which are characterized by malformation of the craniofacial skeleton and the limbs. The major facial features of Nager syndrome include downslanted palpebral fissures, midface retrusion, and micrognathia, the latter of which often requires the placement of a tracheostomy in early childhood. Limb defects typically involve the anterior (radial) elements of the upper limbs and manifest as small or absent thumbs, triphalangeal thumbs, radial hypoplasia or aplasia, and radioulnar synostosis. Phocomelia of the upper limbs and, occasionally, lower-limb defects have also been reported. The presence of anterior upper-limb defects and the typical lack of lower-limb involvement distinguishes Nager syndrome from Miller syndrome (263750), another rare AFD; however, distinguishing Nager syndrome from other AFDs, including Miller syndrome, can be challenging (summary by Bernier et al., 2012).

Gastroschisis is a congenital defect of the abdominal wall that occurs laterally to, and often to the right of, a normally closed umbilical ring. Visceral organs that herniate through the defect are not covered by a membrane. Gastroschisis is distinct from omphalocele (164750), which is characterized by herniation of abdominal contents through the base of the umbilical cord; in omphalocele, the visceral organs are covered by membranes (summary by Mastroiacovo et al., 2007). Both omphalocele and gastroschisis, when they occur without other malformations, are probably multifactorial (Baird and MacDonald, 1981).

Tetraamelia syndrome-1 (TETAMS1) is characterized by complete limb agenesis without defects of scapulae or clavicles. Other features include bilateral cleft lip/palate, diaphragmatic defect with bilobar right lung, renal and adrenal agenesis, pelvic hypoplasia, and urogenital defects (Niemann et al., 2004). Genetic Heterogeneity of tetraamelia syndrome Tetraamelia syndrome-2 (TETAMS2; 618021) is caused by mutation in the RSPO2 gene (610575) on chromosome 8q23.