A previous study indicated that TNF-α, IL-6, IL-8, and IL-17 play a crucial role in the pathogenesis of PV.18, 22 Hence, the authors suggest that IL-29 may up-regulate the expression of cytokines in PBMCs and keratinocytes, and enlarge inflammatory reaction in the pathogenesis of PV. Here, TNF is linked to acquired polycythemia vera.