However, in cases with heavy-chain MM, individuals with a family history of hematologic malignancies were more likely to exhibit IgG kappa MM, with a notable κ light chain restriction (OR 3.23, 95% CI 1.13–9.26; p = 0.029) after the heavy-chain isotype (IgG, IgA) was held constant. This evidence concerns the gene CD79A and hematologic disorder.