Plasmacytoid lymphocytes in SARS‐CoV‐2 infection (Covid‐19)

Abstract

A 59-year-old man with no known past medical history presented to the emergency department with dyspnea, abdominal pain and malaise.Clinical assessment revealed hypoxia with bibasal crepitations on chest auscultation. A chest radiograph showed extensive bilateral air space opacification involving all zones. He was hospitalized with suspicion of infection with the novel coronavirus, SARS-CoV-2, later proven by positive RT-PCR. Blood tests showed multi-organ failure with deranged liver function tests (alkaline phosphatase 611 IU/L, alanine aminotransferase 208 IU/L, gamma-glutamyl transferase 435 IU/L), acute kidney injury (serum creatinine 197 μmol/L), and raised inflammatory markers (C-reactive protein 137 mg/L, ferritin 3303 μg/L). His blood count showed a hemoglobin concentration of 109 g/L, platelet count of 921 × 10 9 /L and total white cell count of 9.8 × 10 9 /L with a neutrophil count of 8.5 × 10 9 /L, and a lymphopenia of 0.9 × 10 9 /L. His blood film showed atypical lymphocytes that appeared reactive. Prominent among these were lymphoplasmacytoid lymphocytes with an eccentric nucleus, deeply basophilic cytoplasm and a prominent paranuclear hof (top and bottom left, ×100 objective). Lymphocytes with prominent cytoplasmic inclusions (Mott cells) were also seen (bottom right). The patient was treated with supplementary high-flow oxygen, intravenous antibiotics and intravenous fluids. He recovered and became oxygen-independent on day 9 post-admission, and was discharged on day 10. The newly emerged pandemic caused by this novel coronavirus presents a challenge to health services across the world. In studies reported from China, lymphopenia was observed in 72 and 85% of patients 1,2 with reduced numbers of T cells (CD4-positive and CD8-positive), B cells and natural killer (NK) cells. 1 A favorable clinical course correlated with an increasing lymphocyte count and improvements in B cell numbers and CD8-positive T cell numbers; multivariate analysis showed an adverse significance of reduced B cells, reduced CD8-positive T cells and an increased CD4/CD8 ratio during the course of the illness. 1

Coronavirus disease 2019 induces multi‐lineage, morphologic changes in peripheral blood cells

“…Our morphologic observations reveal that COVID‐19 is associated with hematologic multi‐lineage changes of all cellular components of the peripheral blood, that is, lymphocytes, monocytes, granulocytes, erythrocytes, and platelets. This is consistent with previous, sporadic reports describing particular aspects like abnormal lymphocytes, plasmocytoid cells, monocytes, granulocytic, or leukoerythroblastic reactions in COVID‐19 patients [15‐18]. Interestingly, while other virus infections (eg, Epstein‐Barr virus or Dengue fever) are known to induce morphologic changes in lymphocytes (termed “reactive lymphocytes” or “virocytes”), these “classical” reactive lymphocytes were found only infrequently in COVID‐19 patients in our study cohort [19,20].…”

“…A low lymphocyte/neutrophil ratio at diagnosis may be even prognostic for developing a severe course of disease [8]. Moreover, some studies report sporadic observations about morphologic changes in peripheral blood like “reactive” or plasmocytoid lymphocytes, abnormal monocytes/granulocytes/thrombocytes, and leukoerythroblastic reaction [15‐18].…”

Peripheral Blood Smear Demonstration of Lymphocyte Changes in Severe COVID-19

“…During viral infection, B-lymphocytes are activated to become lymphoplasmacytoid lymphocytes and immunoglobulin-secreting plasma cells which have a distinctive morphology. [2][3][4] There is emerging evidence that, in addition to elevated inflammatory markers and lymphopenia, elevated lymphoplasmacytoid lymphocytes, which correlate with antibody secreting and CD38 + antigen secreting B-lymphocytes, may predict clinical severity in COVID-19. 4,5 Singapore, and Department of Laboratory Medicine, Alexandra Hospital, Singapore, Singapore, E-mail: winnie_zy_teo@nuhs.edu.sg.…”

Haematological manifestations of COVID‐19: From cytopenia to coagulopathy

“…Examination of the peripheral blood smear remains a crucial part of the haematological assessment and can often aid the diagnosis of many conditions. Notable features reported in COVID‐19 cases include an increased frequency of reactive and plasmacytoid lymphocytes, 13,21 significant left‐shifted granulopoiesis with hypergranular, occasionally vacuolated neutrophils 22 and leucoerythroblastic features 23 . The presence of schistocytes or red cell fragments has not been reported.…”