Swyer-James-MacLeod Syndrome: A Rare Cause of Unilateral Hyperlucent Lung in a Two-Year-Old Male Child.

Swyer-James-MacLeod syndrome (SJMS) is an uncommon post-infectious bronchiolitis obliterans-related pulmonary disorder characterized by a unilateral hyperlucent lung with associated hypovascularity on chest radiography and CT, and markedly reduced perfusion on ventilation-perfusion scintigraphy. Although typically identified in older children or adolescents due to its insidious progression, diagnosis in early childhood remains rare and diagnostically challenging. This report describes a two-year-old male child with recurrent lower respiratory tract infections who was ultimately diagnosed with SJMS based on characteristic radiologic hallmarks. This case emphasizes the importance of maintaining a high index of suspicion for SJMS in young children presenting with persistent or unexplained unilateral pulmonary abnormalities. It highlights the critical role of multimodal imaging in early recognition.