**5.5. Pulmonary Langerhans cell histiocytosis**

Pulmonary Langerhans cell histiocytosis (PLCH) is a rare interstitial lung disease associated with the exposure to tobacco smoke. To provide new insights into its pathogenesis and to compare this disorder with COPD, Ghafouri et al. [39] analyzed BALf from a biopsy-proven case of PLCH, a COPD patient, and a healthy control. Proteins were separated by 2-DE, and their patterns were analyzed with a computerized 2-DE imaging system. If compared with the profiles of the COPD patient and the healthy control, that of PLHC patient lacked significant amounts of protective and anti-inflammatory proteins. These findings opened a new route for a better understanding of the pathophysiology of PLCH.
