Lenalidomide for Adult Histiocyte Disorders

Inclusion Criteria: * Patients must have histologically or cytologically confirmed LCH, ECD or HS. Confirmation of outside pathology at BWH will be performed but is not mandatory prior to study enrollment (see section 3). * Detectable disease by at least one of the following modalities: CT, PET, bone scan, or MRI. * Patients with LCH must require systemic therapy according to the Histiocyte Society LCH Evaluation and Treatment Guidelines (HS 2009) \-- Or * Patients with HS requiring systemic treatment as defined by disease that cannot be surgically resected and/or encompassed in a single radiation field. * Age 18 years or older. * ECOG performance status ≤2 (Karnofsky ≥60%, see Appendix A) * Participants must have normal organ and marrow function as defined below: * absolute neutrophil count ≥1,000/mcL * platelets ≥100,000/mcL * total bilirubin within 1.5 times normal institutional limits * AST(SGOT)/ALT(SGPT) ≤3 × institutional upper limit of normal * creatinine within 2 times normal institutional limits \--- OR * creatinine clearance ≥30 mL/min/1.73 m2. Note, dose adjustments are required for CrCl ≥30 mL/min but ≤60 ml/min. * Able to take aspirin 81 mg daily as prophylactic anticoagulation if not on warfarin, low molecular weight heparin or oral factor Xa inhibitor. Patients intolerant to ASA may use warfarin or low molecular weight heparin at doses designed to treat deep venous thrombosis. * All study participants must be registered into the mandatory…