The presence of isolated IgA or IgM has been reported by Venning, but was not observed in our series [18]. Arya et al. had reported that complement deposition, particularly C3, contributes to the pathogenesis of PV, which was corroborated by our finding of C3 positivity in the DIF-positive PV cases [19]. This evidence concerns the gene CD79A and acquired polycythemia vera.