Amniotic Band Sequence

Abstract

After completing this article, readers should be able to: 1. Identify the clinical spectrum of defects seen in amniotic band sequence. 2. Describe possible mechanisms involved in the formation of defects. 3. Formulate a differential diagnosis for amniotic band sequence. Amniotic band sequence (OMIM #217100) comprises a broad clinical spectrum of defects that includes disruptions, deformations, and malformations. Disruptions may be caused by adhesions or constrictions by amniotic bands of structures programmed to develop normally. Deformations may result from distortion of embryologically normal structures. Amnion rupture may lead to oligohydramnios, which results in fetal constraint and tethering of fetal parts that may cause vascular engorgement, hemorrhage, edema, and tissue necrosis. Malformations may result from the presence of amniotic bands in the early embryonic period that interfere with normal embryogenesis. Amniotic band sequence is also known as amnion rupture sequence, ADAM complex (amniotic deformities/adhesions/mutilations), amniotic band disruption complex, congenital constricting bands, terminal transverse defects, and Streeter anomaly. Amnion rupture sequence has been described clinically as rupture of the amnion followed by encircling of developing structures by strands of amnion. These may vary from constricting bands to limb reduction defects. In addition, deformational defects such as scoliosis or talipes equinovarus may seen. Thoracoabdominoschisis, facial clefts, and encephaloceles also may be associated with amniotic adhesions, ruptured amnion, and amputation defects, and this has been referred to as the Limb Body Wall Complex (LBWC). Several reports regarding the incidence of amniotic band sequence have been cited in the literature. A frequency of 1 in 1,000 for congenital ring constrictions and amputations was reported by Baker and Rudolf. (1) The frequency of amniotic bands has been estimated to range from 1 in 1,234 to 15,000 live births, (2) but may be up to 1 in 56 in previable fetuses. (3) The incidence …