Congenital pulmonary-systemic collateral vein without obstructed left atrial egress is associated with conotruncal anomalies.

We present a case of congenital pulmonary systemic collateral vein associated with truncus arteriosus. Pulmonary systemic collateral vein with nonobstructed left atrial egress is different from those with obstructed left atrial egress in that it is functionally redundant. Including this case, 8 patients among 33 reported cases with pulmonary systemic collateral veins have had nonobstructed left atrial egress. Association with conotruncal anomalies in 4 of these 8 patients, as well as the reported finding that neural crest cells are distributed not only in the conotruncus but also in the cardinal vein, indicates that neural crest cells play roles in remodeling of the systemic venous system.