The observed increase in IgA serum concentration in BP, PF, and LAD as well as the increase of IgG1 and IgG4 in almost all patient cohorts is most likely due to the autoantibody production, as IgA is the predominant Ig in LAD (24), and IgG1 and IgG4 are among the predominant IgG subclasses in PV, PF, and BP (25–27). This evidence concerns the gene CD79A and acquired polycythemia vera.