•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. This evidence concerns the gene CD79A and rheumatoid arthritis.