Advances in our understanding of genetic markers and targeted therapies for pediatric LCH.

Mitogen-activated protein kinase (MAPK) pathway mutation is a hallmark of LCH and is identified in 80% of the cases. Notably, BRAFV600E mutation is seen in ~ 50%-60% of the cases, ~30% has other MAPK pathway mutations, while 15%-20%% have no detected mutations. While the first line therapeutic approach is vinblastine and prednisone, targeted therapies - specifically BRAF/MEK inhibitors - emerged as a promising second-line salvage strategy, particularly when a mutation is identified. Most patients respond to BRAF/MEK inhibitors but at least 75% reactivate after stopping, however, most patients respond again when restarting inhibitors.