Adult Langerhans cell histiocytosis (LCH) usually follows a positive course. Very rarely, LCH involves multiple systems (multiple organ LCH) and is difficult to manage either with the traditional first line treatment (vinblastine, mercaptopurine, prednisone or etoposide) or with 2-chlorodeoxyadenosine. Other treatment modalities have to be used in these patients. We describe a patient with LCH that caused generalized lymphadenopathy and infiltrated pulmonary parenchyma and the skin. The disease activity was always associated with the B symptoms (weight loss, subfebrile states, night sweats). Histological investigations repeatedly showed higher proliferation activity than what is usual in adult patients with LCH. Proliferation marker Ki-67 expression was up to 30% and there were 8–10 mitoses in the field of view of the microscope. Therefore, the treatment started with an application of stimulation regime (cyclophosphamide 2 g/m2 day 1 and etoposide 200 mg/m2 days 1–3) followed by collection of peripheral blood haematopoietic stem cells. Treatment with 2-chlorodeoxyadenosine was then used, first 3 cycles as monotherapy, 5 mg/m2 s.c. days 1–5 in 28-day cycles, and then in combination with cyclophosphamide 150 mg/m2 days 1–5 and methylprednisolone 250 mg days 1–5 during the next 3 cycles. However, the disease relapsed 2 months after the therapy completion. This early relapse was treated with 4 cycles of CHOEP chemotherapy (cyclophosphamide, doxorubicin, etoposide, prednisone). High dose BEAM (BCNU, cytosine-arabinoside, etoposide, melphalan) chemotherapy followed after the 4th cycle with autologous stem cell transplantation. According to the follow up PET-CT, this treatment resulted in complete remission. However, the disease relapsed again in lymph nodes, lungs, skin and bones 5 months after the high dose chemotherapy. The progression was documented by PET-CT. Lenalidomide 25 mg daily for 21 days in 28-day cycles with dexamethasone 20 mg once a week were administered as the 4th line treatment. The 4th cycle of lenalidomide was followed by PET-CT. CT suggested a significant reduction (> 50 %) in lymph node size. PET showed a significant reduction in fluorodeoxyglucose accumulation in the affected lymph nodes as well as bone lesions. HRCT showed regression of pulmonary nodules. During the treatment, CRP levels declined and haemoglobin value rose from 110 to 141 g/l, i.e. partial remission was achieved after 4 cycles. Etoposide (100 mg i.v.) was added to lenalidomide and dexamethasone on days 22, 23 and 24 of the above mentioned 28-day cycle. Addition of etoposide furthered treatment response. The total of 11 cycles of this chemotherapy resulted, according to a follow up PET-CT, in complete remission. The achieved remission was consolidated using allogeneic bone marrow transplantation after FLAMSA reduced density conditioning without amsacrine. Four months after allogeneic transplantation the patient is free of relapse. We showed treatment response of highly aggressive LCH to lenalidomide. Four cycles have led to partial remission and treatment response was furthered with the combination of lenalidomide, dexamethasone and etoposide to complete remission.