Hay at the End of a Bridge: A Rare Case of Proximal Interruption of the Pulmonary Artery with Ipsilateral Interstitial Lung Disease

Proximal interruption of the pulmonary artery, also referred to as unilateral absence of the pulmonary artery (UAPA), is a rare congenital anomaly resulting from abnormal embryogenesis of the sixth aortic arch. It is frequently misdiagnosed due to nonspecific clinical features and overlapping radiological findings with more common pulmonary conditions. This case report presents the case of a 40-year-old woman with progressive exertional dyspnea and recurrent respiratory infections, in whom radiological evaluation revealed a complete absence of the left pulmonary artery with systemic collateral supply and associated interstitial lung disease of the left lung. This case underscores the importance of considering UAPA in the differential diagnosis of unilateral lung pathology and highlights the role of timely recognition in reducing morbidity.