BRAF and Langerhans cell histiocytosis: At multivariable analysis, age at diagnosis (HR 1.052, 95% CI 1.008-1.096), associated hematologic conditions (HR 3.030, 95% CI 1.040-8.827), and treatment failure (HR 9.736, 95% CI 2.919-32.481) were associated with an increased risk of death, while lytic bone lesions with a lower risk (HR 0.116, 95% CI 0.031-0.432).<h4>Interpretation</h4>Mixed ECD-LCH is a multisystem disease driven by the <i>BRAF</i><sup><i>V600E</i></sup> mutation and targeted treatments are effective.