COVID-19 and Hematological Manifestations

COVID-19, the disease caused by SARS-CoV-2, is characterized by significant abnormalities of the hematopoietic as well as the hemostatic system. These abnormalities have important prognostic as well as therapeutic implications in the management of these patients. Lymphopenia has emerged as a cardinal manifestation of COVID-19, which correlates with the severity of the cytokine storm and confers an adverse prognosis. Although not associated with direct cytopathic effects of SARSCoV- 2, anemia and thrombocytopenia are commonly present, with increased incidence in critically ill patients. It has been suggested that an ineffective adoptive immune response may be responsible for the hyper-inflammatory state and cytokine response in patients with severe COVID-19. Dysregulation of the macrophage phenotype may be associated with secondary HLH like physiology with hyperferritinemia and multi-organ dysfunction. The coagulation abnormalities are characterized by normal or elevated fibrinogen levels and are distinct from DIC. This distinct coagulopathy is labelled as COVID coagulopathy. It is predominant due to local microangiopathy and endothelial dysfunction in involved organs, such as the pulmonary vasculature. The hypercoagulable state is associated with a higher risk of arterial and venous thrombosis and a trend towards an increase in vaso-occlusive events, such as myocardial infarction and stroke. The D-Dimer elevation is seen in approximately 50% of patients, and increasing value during hospitalization indicates a poor prognosis. Finally, a comprehensive understanding of these pathophysiological states may help us in devising treatment protocols with a combination of antiviral, anti-inflammatory, and anticoagulation strategies for best treatment outcomes.