Evolution and regression of imaging findings in treated pulmonary Langerhans cell histiocytosis.

In rare instances, pediatric Langerhans cell histiocytosis (LCH) may manifest as lung disease. While the imaging features at presentation have been reported, we present sequential computed tomography (CT) scans of a 3-year-old boy with pulmonary LCH, revealing the evolution and regression of the disease. Sequential CT scans during treatment demonstrated variable evolution of pulmonary cysts, including changes in size, thinning of walls, and a pattern of collapse into irregular nodules and involution. Our case represents a rare opportunity to examine sequential CT findings of pediatric pulmonary LCH regression.