Bone Marrow Suppression and Hemophagocytic Histiocytes Are Common Findings in Korean Severe Fever with Thrombocytopenia Syndrome Patients

The causes of cytopenia in patients with severe fever with thrombocytopenia syndrome (SFTS) are not fully understood until now. We reviewed the bone marrow (BM) findings of patients with SFTS to unravel the cause of the cytopenia. Three Korean SFTS were enrolled in this study. Thrombocytopenia, neutropenia, and anemia were detected in all three patients. Severe hypocellular marrow (overall cellularity <5%) and a decreased number of megakaryocytes were noted in one patient, and hypo-/normocellular marrow and an increased number of hemophagocytic histiocytes were observed in two patients. Megakaryocytes were relatively preserved in two patients. Although a limited number of cases are available, our observations suggest that both BM suppression and peripheral destruction or sequestration are causes of cytopenia of patients with SFTS. To the best of our knowledge, this is the first well documented pathologic evaluation of Korean SFTS.