Bone Marrow and Peripheral Blood Findings in Patients Infected by SARS-CoV-2

Abstract

Objectives: Coronavirus disease 19 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is associated with diverse clinical, including hematologic, abnormalities. We describe peripheral blood and bone marrow findings in deceased and living patients with COVID-19.

Methods: We examined bone marrows from 20 autopsies and 2 living patients with COVID-19 using H&E-stained slides and immunohistochemical stains. Clinical history and laboratory values were reviewed. HScore was calculated to estimate risk of hemophagocytic lymphohistocytosis (HLH).

Results: The deceased patients included 12 men and 8 women (aged 32 to >89 years; median, 63 years). Hematologic abnormalities included frequent neutrophilic leukocytosis, lymphopenia, anemia, and thrombocytopenia; one patient showed striking erythrocytosis. The bone marrows were all normocellular to hypercellular, most showing maturing trilineage hematopoiesis with myeloid left shift. In all 19 evaluable bone marrows, hemophagocytic histiocytes were identified. The HScore for secondary HLH ranged from 35 to 269 (median, 125; >169 in 5 patients). Coinfections were identified in 6 patients. In 2 living patients, bone marrow showed maturing trilineage hematopoiesis, including one showing few hemophagocytic histiocytes.

Conclusions: Peripheral blood from deceased patients with COVID-19 frequently showed neutrophilic leukocytosis, lymphopenia, and, rarely, secondary polycythemia; hemophagocytosis was common in their bone marrow. Consistent with other studies, we provide histopathologic evidence of secondary HLH development in patients with COVID-19.

Keywords: Bone marrow; CBC; COVID-19; Coronavirus; Hemophagocytosis; Peripheral blood; SARS-CoV-2.

Figure 1

Hematologic data on admission and last CBC before death for the 17 patients with in-house autopsy. Gray bar demonstrates normal range for WBC count (P = .0036) (A), absolute neutrophil count (ANC; P = .0042) (B), absolute lymphocyte count (ALC) (C), absolute monocyte count (AMC) (D), hematocrit (P = .0007) (E), and platelets (F).

Figure 2

Hematologic data on admission and last CBC before death for the 6 patients with in-house autopsy and coinfections. Gray bar demonstrates normal range for WBC count (P = .0107) (A), absolute neutrophil count (ANC) (B), absolute lymphocyte count (ALC) (C), absolute monocyte count (AMC) (D), hematocrit (P = .0312) (E), and platelets (F).

Figure 3

A, Low power shows bone marrow that is hypercellular for age. B, Higher power shows trilineage hematopoiesis with maturing myeloid and erythroid elements, with a leftward shift in myeloid maturation. A large histiocyte with phagocytosis of multiple RBCs is seen at the center of the image (C, oil immersion). An immunostain for CD68 (D) shows scattered hemophagocytic histiocytes (arrows); the inset shows 1 hemophagocytic histiocyte with engulfed leukocytes (oil immersion).