Given that the exonic polymorphism p.D48A (or rs3816527) in the PTX3 gene forms with rs2305619 in intron 1 and rs1840680 in intron 2 an haplotypic block that has been linked to the susceptibility to selected infections as well as different circulating levels of the protein, it was important to assess whether this amino acid substitution had any effect on C1q recognition. The gene discussed is PTX3; the disease is infection.