Spontaneous regression of pulmonary involvement after smoking reduction and removal of and radiation therapy for Langerhans cell histiocytosis of the sphenoid bone: which comes first, the chicken or the egg?

Isolated pulmonary Langerhans cell histiocytosis (LCH) in adults is known to regress spontaneously after smoking cessation alone, but little is known about whether this rationale could also apply in cases of multisystem pulmonary LCH. In particular, pediatric patients with multisystem LCH including involvement in "risk organs" such as lungs often benefit from systemic chemotherapy. Here, we present a 37-year-old man with spontaneous regression of pulmonary lesions in multisystem LCH, achieved solely by smoking reduction following local treatment of bone lesions.