To test if the citrullination of myosin-9 and the myosin light chains result in immunogenic epitopes recognized by ACPA in patients with RA, we screened sera from 30 patients with RA and 20 healthy controls (HC) for IgG autoantibodies against citrullinated peptides corresponding to myosin-9 residues R867, R1703, R1888, and R1912, as well as R94 of MYL6 and R132 of MYL12A. The gene discussed is PRTN3; the disease is rheumatoid arthritis.