RecruitingPhase 2Drug trialOptimization of the Time and Dosage of Trametinib in BRAF Negative Juvenile PatientsProspective, interventional, open, randomized, single-center, non-commercial clinical trial to optimize treatment and dosage of trametinib in juvenile patients with histiocytosis resistant to conventional therapy and without the BRAF gene mutation or after the failure of vemurafenib treatment.