Introduction. Systemic mastocytosis is a heterogeneous group of hematological disorders characterized by accumulation of mast cells in different organs. Case report. A 41-year-old woman presented with a three-year history of fatigue, occasional diarrhea, mild fever, skin rash and splenomegaly. Laboratory results showed severe anemia and thrombocytopenia. Cytological and histological investigation of bone marrow showed a marked increase of mast cells infiltration with following immunophenotype: CD117+, CD68+, CD34-, MPO-, CD15-. She was treated with cladribine 0.15 mg/kg body weight from day 1 to day 5, a total of six cycles, and achieved a good partial response, transfusion independency and normalization of spleen size. Although the patient responded to the treatment, the relapse with splenomegaly and bicytopenia was observed after 10 months. Conclusion. Cladribine therapy was efficient in the patient' with systemic mastocytosis but the response was transient, so there is the need to search for new therapeutic options and more effective strategies in the treatment of patients with aggressive mast cell disorders.