Pulmonary Langerhans Cell Histiocytosis That Progressed from a Single-system to a Multisystem Form despite Smoking Cessation

A 36-year-old Japanese man presented with cavities and nodular shadows in the lower lobes of his lungs and osteolytic lesions in the thoracic spine. He was diagnosed with multisystem Langerhans cell histiocytosis (LCH). Three years earlier, he had been noted to have small cavities and granular lesions noted in the upper lobes of his lungs, which later improved with smoking cessation. It was likely that his single-system pulmonary LCH (PLCH) progressed to multisystem LCH despite smoking cessation. Relapse or progression may occur in cases where PLCH lesions improve after smoking cessation. Thus, close follow-up is vital.