Between 57 and 75% of patients with ECD carry the BRAFV600E mutation, an activating mutation of the proto-oncogene BRAF. More than 50 patients worldwide with BRAF mutations and severe multisystem refractory ECD (sometimes accompanied by Langerhans cell histiocytosis, LCH) have received vemurafenib. Here, BRAF is linked to Langerhans cell histiocytosis.