Recent advances in Langerhans cell histiocytosis.

The purpose of this review is to provide an updated overview of the pathogenesis and treatment of Langerhans cell histiocytosis (LCH). The pathogenesis of LCH remains obscure and the optimal treatment for LCH has not been established, although incremental progress has been made. Proinflammatory cytokines and chemokines are known to play a role in LCH, which suggests that LCH is an immune disorder. However, the oncogenic BRAF mutation is also detected in more than half of LCH patients, which suggests that LCH is a neoplastic disorder. Remaining major issues in the treatment of LCH are how to rescue patients who have risk-organ involvement but do not respond to first-line therapy, the optimal treatment for the orphan disease of multifocal adult LCH, and how to reduce and treat central nervous system-related consequences, such as central diabetes insipidus and neurodegeneration. More research is needed to better understand the pathogenesis of this disease and to resolve the treatment issues.