Detection of an NRAS mutation in Erdheim-Chester disease

To the editor: In a recent paper in Blood , Haroche et al reported dramatic efficacy of vemurafenib in 3 cases of multisystem and refractory Erdheim-Chester disease (ECD) and Langerhans cell histiocytosis harboring the BRAF V600E mutation.[1][1] The findings of an ∼50% prevalence of BRAF