No significant differences in CMV IgG seropositivity (13/4 vs. 17/3, pos./neg., PV vs. controls, Fisher’s exact P=0.68), serum CMV IgG levels [median (IQR): 145 (29–185) vs. 136 (72–184) AU/mL, PV vs. controls, P=0.866], and CMV IgM seropositivity (1/16 vs 0/18, pos./neg., PV vs. controls, Fisher’s P=0.485) were noticed either. The gene discussed is CD40LG; the disease is acquired polycythemia vera.