•Serum anti-MAA IgA Ab (not IgG/IgM) increased in RA-high CAC vs. RA-low CAC•Positive correlations of IgA anti-MAA with insulin resistance (rho = 0.18, p = 0.03), inverse correlations with HDL (rho = -0.20, p =0.01)•Anti-MAA IgA improved 10-yr risk prediction of high CAC. The gene discussed is CD79A; the disease is Insulin resistance.