Idiopathic isolated pulmonary artery aneurysm: a case report.

Background: Pulmonary artery aneurysms (PAAs) are rare vascular anomalies, most commonly associated with pulmonary hypertension, congenital heart disease, vasculitis, or infection. Idiopathic PAAs, lacking an identifiable underlying cause, are exceptionally rare and often discovered incidentally. This case illustrates the diagnostic approach and rationale for conservative management of idiopathic PAAs in the absence of high-risk features. Case Summary: We describe a 70-year-old female with a history of asthma, obstructive sleep apnoea, and transient ischaemic attack, in whom a PAA was incidentally discovered following imaging for respiratory complaints. Contrast-enhanced computed tomography (CT) revealed a fusiform aneurysm of the left lower lobe pulmonary artery, with a maximum axial diameter of 4.6 cm, located just distal to the origin of the lower lobe branch from which also the lingula artery arises. Retrospective comparison with a chest radiograph from 10 years earlier confirmed interval growth. There were no clinical or imaging features suggestive of pulmonary hypertension, congenital shunts, or significant valvular disease, nor any clinical or biochemical evidence of infection, connective tissue disease, or vasculitis. Multidisciplinary evaluation supported the diagnosis of an idiopathic and acquired pulmonary aneurysm. A conservative approach with follow-up CT imaging at 6 months, which demonstrated stability of aneurysm size and morphology, was chosen. Discussion: This case underscores the importance of recognizing rare vascular anomalies in patients with non-specific respiratory symptoms. In the absence of an identifiable underlying pathology, an idiopathic cause should be considered. Conservative management may be appropriate in selected cases lacking high-risk features, though long-term outcomes remain uncertain.