An association between the presence of periodontitis and ACPA or IgM-RF levels or both could not be established, in contrast to the findings of Dissick and colleagues [2], nor could we find differences in reactivity to the five synthetic citrullinated peptides between the DPSI categories, other than a higher reactivity against citrullinated peptide fibrinogen-2 in P. gingivalis culture-positive patients. The gene discussed is PRTN3; the disease is periodontitis.