A 7-year-old previously healthy Czech boy was admitted due to fever, hepatosplenomegaly and pancytopenia. Aspiration of bone marrow revealed no signs of hemoblastosis (nor hemophagocytosis). He was treated with antibiotics and virostatics without effect. Progression of hepatospenomegaly and pancytopenia induced suspicion of hemophagocytic lymphohistiocytosis (HLH). Five weeks later, bone marrow hemophagocytosis of erythrocytes, nuclear elements and platelets was detected. He was given corticoids and intravenous immunoglobulins and transferred to our haematology department. Laboratory findings of mild pancytopenia, hypofibrinogenaemia, hyperlipidaemia and elevated levels of ferritin, LDH and immunoglobulins were compatible to the diagnosis of HLH. Immunologic evaluation revealed T-lymphocyte activation. Appropriate immunosuppressive treatment with Dexamethason, etoposide and Cyclosporine A was launched, followed by transient subside of fever and improvement of peripheral blood count, but not regression of hepatosplenomegaly. Four weeks later, relaps of fever and deterioration of blood count led to intensification of immunosuppression. However, no effect was evident.Moreover, hypertrophic cardiomyopathy with ventricular arytmia occurred. Treatment with antilymphocytic globuline for resistant course of HLH was planned. Before that, a fifth bone marrow aspiration was performed. Surprisingly, many Leishmania amastigotes were observed within marrow macrophages. Leishmania infection was confirmed by positive serology. Immunosuppressive treatment was withdrawn and changed for causal treatment with liposomal Amphotericine B. Positive clinical effect with subside of fever was evident in ten days, splenomegaly gradually resolved during three weeks, restoration of normal blood count lasted six weeks. No relapses of HLH nor leishmaniasis occurred. In control bone marrow aspirate performed three months later, the parasites were not detected. Ten months after the event, the patient is in complete remission of HLH with normal immunologic parameters. Most probably, he contracted visceral leishmaniasis during a visit of a Neapol area in Italy 3 months before the onset of the disease.

        Key words: hemophagocytic syndrome, visceral leishmaniasis.