Left pulmonary artery atresia and MAPCA aneurysm.

Unilateral atresia of the pulmonary artery (UAPA) is a rare condition often associated with congenital cardiac anomalies, such as tetralogy of Fallot or septal defects. UAPA is linked to an altered development of the sixth aortic arch segment, resulting in the proximal interruption of the pulmonary artery and it often occurs on the side of the chest opposite the aortic arch [1]. As a compensatory mechanism, major aortopulmonary collateral arteries (MAPCAs) arise from systemic arteries to supply distal intrapulmonary branches of the atretic pulmonary artery. MAPCAs can originate from various vessels, including the descending aorta, bronchial, intercostal, internal mammary, subclavian, or even coronary arteries. Patients with UAPA may present with diverse clinical symptoms, including chest pain, pleural effusion, recurrent infections, dyspnea, exercise intolerance, and hemoptysis [1, 2]. Chest radiographs reveal characteristic features: asymmetric lung fields with a small, hyperlucent lung with a raised diaphragm on the affected side, and an ipsilateral shift of the mediastinum. Extensive transpleural collateral circulation may mimic tuberculosis on plain films. CT and MRI allow direct visualization of the absent pulmonary artery and associated cardiac anomalies. A CT scans often show collateral vessels, mosaic parenchymal changes, and bronchiectasis due to recurrent infections in the affected lung [2].