IFNG and secondary hemophagocytic lymphohistiocytosis: Within the subset of severe COVID-19, there is increasing evidence for a hyperinflammatory response similar to that seen in cytokine storm syndromes (CSS) and secondary hemophagocytic lymphohistiocytosis (sHLH), characterized by thrombocytopenia, lymphopenia, elevated D-dimer levels, low fibrinogen, elevated lactate dehydrogenase (LDH), elevated liver enzymes, elevated ferritin, and elevation in cytokine/chemokine levels—including IL-1β, IL-6, IL-18, and interferon-gamma (IFNγ) [2].