APCU25MPA1 Vanished vessel: a case of unilateral absence of left pulmonary artery in a 34-year-old filipino male presenting with dyspnea on exertion: a case report

Introduction Unilateral absence of pulmonary artery (UAPA) is a rare cardiovascular anomaly and may remain undiagnosed until adulthood, presenting with nonspecific symptoms such as dyspnea, recurrent respiratory infections, or pulmonary hypertension. Documented case reports of isolated UAPA are limited, complicating both diagnostic evaluation and management. This case highlights the uniqueness of the condition and emphasizes the need for awareness and comprehensive cardiovascular evaluation in patients presenting with unexplained dyspnea.Case Presentation We report a case of a 34-year-old Filipino male with a 2-year history of progressive exertional dyspnea initially attributed to gastroesophageal reflux disease. Initial evaluation revealed cardiomegaly, ascites, right-sided chamber enlargement, severe tricuspid regurgitation, moderate pulmonary hypertension, and moderate pericardial effusion. Transesophageal echocardiography and cardiac magnetic resonance imaging (MRI) demonstrated the absence of the left pulmonary artery with collateral supply from the descending aorta. Hemodynamic studies confirmed pulmonary hypertension in the absence of an intracardiac shunt. Coronary angiography revealed normal coronary arteries. The patient was managed medically with activity restriction and discharged in improved and stable condition.Discussion UAPA is a rare anomaly affecting a single pulmonary artery, most often the left, with an estimated incidence of 1 in 200,000 individuals. The anomaly results from agenesis of the sixth aortic arch segment during embryogenesis, leading to absence of the proximal pulmonary artery and development of systemic-to-pulmonary collaterals. Patients may remain asymptomatic for years. Right chamber dilation from volume and pressure overload contributes to tricuspid regurgitation. Pulmonary hypertension develops secondary to increased pulmonary vascular resistance in the single functioning pulmonary artery. Accurate diagnosis relies on multimodality imaging. Cardiac MRI provides detailed anatomical visualization confirming the absence of the pulmonary artery. Pulmonary angiography remains the gold standard for definitive assessment of vascular anatomy and collateral circulation. Management is guided by symptom severity and presence of pulmonary hypertension, with medical therapy for pulmonary hypertension and heart failure as the mainstay.Conclusion This case illustrates the diagnostic challenge of UAPA in adults with atypical presentations. Comprehensive multimodality imaging is essential for accurate diagnosis and management planning. Early recognition is critical to prevent complications such as pulmonary hypertension and right-sided heart failure.