Heterotaxy, Visceral, 4, Autosomal, also known as left-right axis malformations, is related to contractures, pterygia, and spondylocarpotarsal fusion syndrome 1a and visceral heterotaxy. An important gene associated with Heterotaxy, Visceral, 4, Autosomal is ACVR2B (Activin A Receptor Type 2B). Affiliated tissues include spleen and liver, and related phenotypes are atrioventricular canal defect and midline liver