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

Abstract

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.

Keywords: Korea; Severe fever with thrombocytopenia syndrome bunyavirus; bone marrow.

Fig. 1. Findings of bone marrow (BM) aspirate and section of case 1 (A, B, and C), 2 (D and E), and 3 (F, G, and H). (A) The hemophagocytic histiocytes were increased in the aspirate [Wright-Giemsa (W-G), ×400]. (B) Hypocellular area was noted in the BM section [hematoxylin and eosin (H&E), ×100]. (C) The number of dysplastic megakaryocytes increased slightly in the cellular area (CD61 immunohistochemistry, ×400). (D) Hypocellular particles (W-G, ×40) are noted. (E) Severe hypocellular marrow is noted (H&E, ×40). (F) The hemophagocytic histiocytes are increased in the aspirate (W-G, ×400). (G) Megakaryocytes are normally observed in the aspirate (W-G, ×200). (H) Normocellular marrow for age (86 years) with a focally hypocellular area is noted (H&E, ×100).