Left pulmonary artery sling: difference in monochorionic monoamniotic twin presentation.

Pulmonary artery sling (PAS) is a rare congenital vascular anomaly where the left pulmonary artery (LPA) originates from the right pulmonary artery and passes between the trachea and esophagus. Limited literature has been published about PAS in twins. This report demonstrates two different outcomes in mono-mono twins presenting with PAS. Patients with PAS can experience sequelae including wheezing, stridor, atelectasis, or emphysema. Vascular rings occur when the anomalous LPA encircles the airway and esophagus, causing direct compression and respiratory distress. In the case of LPA sling, the sling does not encircle the airway and esophagus but acts as a cradle so the airway which is adjacent to the vessel is not directly compressed. Unfortunately, patients with LPA sling may become severely ill due to airway narrowing even when there is no compression of the adjacent airway. This is the more common presentation in PAS and was seen in Twin A whereas direct airway compression was seen in Twin B. PAS usually presents in patients during their first year of life and high clinical suspicion is important for diagnosis. As this case report demonstrates, presentations and outcomes can be variable in mono-mono twins with LPS and as a result, appropriate investigations should be offered with monitoring of respiratory compromise.