PRF1 and hereditary hemophagocytic lymphohistiocytosis: Of particular relevance is PRF1 gene (Supplementary Material, Table S3), in which some mutations encode a shorter perforin protein, unable to carry out its role of cell destruction and immune system regulation, leading to the exaggerated immune response (HP:0002958, HP:0003256, HP:0030356, HP:0011112, HP:0011118, HP:0002958, HP:0030783 and HP:0004313) characteristic of familial hemophagocytic lymphohistiocytosis (57), condition that could aggravate the COVID-19 infection response, leading to the cytokine storm and to severe COVID-19 (58).