Pulmonary Langerhans cell histiocytosis commonly affects young adult smokers. History, clinical symptoms and imaging findings are the key to diagnosis.

The imaging findings show a specific distribution of reticulonodular pattern opacities and cystic lesions as seen in this case. However definitive diagnosis is made by lung biopsy.

In this case, the presence of a lytic bony lesion supports the diagnosis of pulmonary Langerhans cell histiocytosis.