Abstract
BACKGROUND: The clinical presentation of coronavirus disease 19 (COVID-19) is the result of intricate interactions between the novel coronavirus and the immune system. In patients with hematologic malignancies (HM), these interactions dramatically change the clinical course and outcomes of COVID-19. SUMMARY: Patients with HM and COVID-19 are at an increased risk for prolonged viral shedding, more protracted and severe presentation, and death, even when compared to other immunocompromised hosts. HM (e.g., multiple myeloma, chronic lymphocytic leukemia) and anticancer treatments (e.g., anti-CD20 agents) that impair humoral immunity markedly increase the risk of severe COVID-19 as well as protracted viral shedding and possibly longer infectivity. Cytokine release syndrome (CRS) is an important player in the pathophysiology of severe and fatal COVID-19. Treatments targeting specific cytokines involved in CRS such as interleukin-6 and Janus kinase have proven beneficial in COVID-19 patients but were not assessed specifically in HM patients. Although neutropenia (as well as neutrophilia) was associated with increased COVID-19 mortality, granulocyte colony-stimulating factors were not beneficial in patients with COVID-19 and may have been associated with worse outcomes. Decreased levels of T lymphocytes and especially decreased CD4+ counts, and depletion of CD8+ lymphocytes, are a hallmark of severe COVID-19, and even more so among patients with HM, underlying the important role of T-helper dysfunction in severe COVID-19. In HM patients with intact cellular immunity, robust T-cell responses may compensate for an impaired humoral immune system. Further prospective studies are needed to evaluate the mechanisms of severe COVID-19 among patients with HM and assess the efficacy of new immunomodulating COVID-19 treatments in this population. KEY MESSAGES: Understanding the immunopathology of COVID-19 has greatly benefited from the previous research in patients with HM. So far, no COVID-19 treatments were properly evaluated in patients with HM. Patients with HM should be included in future RCTs assessing treatments for COVID-19.