Overall, patients with severe COVID-19 infection may present with typical features of macrophage activation syndrome which is partly resulting from overwhelming IFNγ formation (Webb et al., 2020) as reflected by higher levels of the IFNγ-inducible macrophage-derived biomarker neopterin in subjects with severe COVID-19 (Bellmann-Weiler et al., 2021). This evidence concerns the gene IFNG and macrophage activation syndrome.