CRP and isolated hyperferritinemia: Although the pathophysiological relationship between severe COVID-19 and sHLH is not well-defined, a series of studies suggest that some patients with severe COVID-19 could develop sHLH, these patients exhibiting a hyperinflammatory state, like that of sHLH of other causes, such as elevated C reactive protein, hyperferritinemia, altered liver function, and coagulopathy, expressed by increased serum levels of D-dimers [21-24].