Image Quiz: Unilateral Hyperlucent Lung in a Young Adult

A young adult with chronic cough and sputum presented with a unilateral hyperlucent lung on chest imaging, with computed tomography (CT) pulmonary angiography findings consistent with Swyer–James–MacLeod syndrome (SJMS). This rare postinfectious sequela of childhood bronchiolitis, often following adenoviral infection, results in obliterative bronchiolitis with air-trapping and reduced perfusion. Radiologically, SJMS is characterized by unilateral hyperlucency, a small ipsilateral pulmonary artery, and mosaic attenuation on CT, and must be carefully distinguished from congenital pulmonary anomalies to ensure accurate diagnosis and management.