C68-26 No Artery, No Party: When Left Pulmonary Artery Agenesis Invites a Mycobacterial Guest

Abstract Introduction Cavitary pulmonary disease presents a diagnostic challenge, especially in individuals from tuberculosis-endemic regions. While nontuberculous mycobacteria (NTM) are increasingly recognized as important pathogens, their occurrence in the setting of congenital pulmonary vascular anomalies—particularly unilateral pulmonary artery agenesis (UPAA)—remains exceedingly rare, with only isolated reports in the literature. This case underscores a potential pathophysiologic link between congenital hypoperfusion and susceptibility to opportunistic infection. Case Report A 44-year-old female, non-smoker who works as a fitness instructor. She immigrated from Ecuador in 2021 who initially presented with a 3-week history of productive cough, mild hemoptysis, and left upper back pain. She denies any dyspnea on exertion. Chest x-ray revealed patchy opacities with cavitary changes in the left upper lobe. CT angiography of the chest demonstrated cavitary lesions in the left upper and superior lower lobes with tree-in-bud nodularity throughout the left lung, alongside right upper lobe opacities. Notably, the left pulmonary artery was absent, with only a diminutive atretic remnant in the expected anatomical course; the right pulmonary artery was intact (Image 1). Baseline laboratory testing was unremarkable with a WBC of 7.3 K/UL, D-dimer of 449 ng/mL, QuantiFERON-TB Gold and Mycobacterium tuberculosis PCR were negative. Pneumonia workup including MSSA/MRSA, urine for Legionella/S. pneumoniae, rapid viral testing and HIV were also all negative. However, three sputum samples were smear AFB-positive, and culture confirmed Mycobacterium intracellulare, establishing a diagnosis of Mycobacterium avium complex (MAC) pulmonary infection. The patient was started on azithromycin, rifampin, and ethambutol and is now following with infectious disease clinic. She was advised to avoid inhaled corticosteroids due to the risk of recurrent infection in hypoperfused lung regions and scheduled for close pulmonary follow-up. Discussion UPAA results from failed development of the sixth aortic arch, leading to unilateral absence of pulmonary arterial flow and chronic lung hypoplasia. Chronic hypoperfusion results in impaired mucociliary clearance, ventilation-perfusion mismatch, and reduced local immune defense, potentially predisposing to NTM infection. In such patients, hemoptysis may arise from parenchymal destruction or rupture of hypertrophied systemic collaterals. While no guidelines exist for UPAA-associated NTM infection, early recognition may prevent complications such as bronchiectasis, recurrent infection, or pneumothorax. In refractory cases, hemi-pulmonectomy has been described. This case highlights congenital unilateral pulmonary artery agenesis as an underrecognized host risk factor for NTM infection and emphasizes the importance of considering structural vascular anomalies in atypical cavitary lung disease. This abstract is funded by: None