Hemophagocytic syndrome: a rare complication of allogeneic nonmyeloablative hematopoietic stem cell transplantation.

We report two cases of patients with malignant lymphoma who presented with early onset of hemophagocytic syndrome after nonmyeloablative allogeneic peripheral blood stem cell transplantation. Fever and skin eruption developed early after transplantation, and neurological symptoms preceded cytopenia and worsened progressively. Activated macrophages with hemophagocytosis were found in bone marrow of the two patients at day 15 and 56, respectively. The fact that no obvious infectious agents associated with hemophagocytic syndrome were detected, and that serum soluble interleukin-2 receptor concentrations were elevated in the early phase after transplantation, reflecting the activation of donor-derived T cells, suggests that this complication resulted from an alloimmune response.