Severe pulmonary hypertension in histiocytosis X: long-term improvement with bosentan.

Pulmonary Langerhans’ cell histiocytosis (LCH)/histiocytosis X is a rare smoking-related interstitial lung disease that predominantly affects adults aged 20–40 yrs. It is commonly associated with irreversible airflow obstruction and highly variable clinical outcomes. The disease may regress spontaneously or following smoking cessation; however, in 20–30% of cases it progresses to chronic respiratory insufficiency. Despite encouraging results in case series and reports [1], no established efficacy on disease outcomes has been demonstrated with corticosteroids, vinblastine or cladribine.