Research on MAS and COVID-CS has found substantially different clinical features and laboratory parameters, such as hyperferritinemia and serum CRP levels in severe cases of COVID-19 being lower than in MAS, while the levels of the most important cytokines IL -1, IL-6, IL-18, etc., have lung-specific immune characteristics, different from a typical CSS [141,188,189]. Here, CRP is linked to macrophage activation syndrome.