Langerhans cell histiocytosis (LCH) is a rare disorder of Langerhans cell with unknown etiology, which can uncommonly be associated with pneumothorax.

A 14-month-old female is presented here who was referred to our center due to acute respiratory distress. Reticulonodular changes with multiple cystic areas were detected in chest X-ray, whilst extensive honeycombing and cystic changes were seen in high-resolution computed tomography scan. With deterioration of respiratory distress, chest X-ray was repeated, which revealed a unilateral pneumothorax. Meanwhile, some hyperpigmented skin plaques appeared on her skull and back. The biopsy results confirmed the diagnosis of proliferative histiocytosis. Prompt diagnosis of LCH and initiation of appropriate treatment in the patients who present with pneumothorax are vital to prevent further complications and even death in this group of patients. Keywords : histiocytic infiltration, Langerhans cell histiocytosis, pneumothorax