Recurrent Haemoptysis caused by a Rare Systemic Artery to Pulmonary Artery Fistula: A Case Report

Abstract Background Recurrent haemoptysis is a common but diagnostically challenging presentation in medicine. While infection, malignancy, and pulmonary embolism constitute the frequent differentials, rare vascular anomalies such as systemic artery to pulmonary artery fistula (SA-PAF) may occasionally underlie persistent or unexplained cases. Early recognition is essential to prevent morbidity from chronic haemorrhage, pulmonary hypertension, or high-output cardiac failure. Case Presentation A 26-year-old woman presented with progressive haemoptysis over 12 years. She had no prior history of trauma, pulmonary infections, or systemic disease. Initial investigations, including chest radiography, haematological parameters, and autoimmune screening, were unremarkable. Echocardiography demonstrated normal left ventricular function without pulmonary hypertension. Given the persistence of symptoms and normal conventional imaging, CT thorax was performed and suggested bronchiectatic changes; however, subsequent CT bronchial angiography identified a vascular tuft in the left lower lobe, supplied by an anomalous branch of the left inferior phrenic artery draining into a pulmonary artery segment. The findings were consistent with a systemic artery to pulmonary artery fistula. The patient underwent successful endovascular embolisation with complete resolution of haemoptysis on follow-up. Discussion This case underscores the importance of maintaining a broad differential in patients with recurrent haemoptysis, particularly when initial investigations fail to yield a cause. Although SA-PAF is a rare entity, it can mimic more common pathologies such as tuberculosis-related bronchiectasis, especially in endemic regions. Conventional imaging modalities may not always detect subtle vascular abnormalities, and escalation to CT angiography should be considered early when clinical suspicion persists. Timely identification permits minimally invasive management, averting potential complications such as irreversible pulmonary hypertension or high-output cardiac states. Continued surveillance remains advisable given the theoretical risk of recurrence or new collateral formation.