PTX3 and Opportunistic infection: Three common single-nucleotide polymorphisms (SNPs) in the PTX3 gene (namely, rs2305619, rs3816527, and rs1840680) have been associated with the concentration of the PTX3 protein in biological fluids (i.e., plasma and BAL [18,19]), the risk of opportunistic infections of bacterial [12,20,21] and fungal [19,22,23] etiology, and the severity of COVID-19 disease [24].