Matching Pairs polycythemia veraOnline version information about thus blood cancer by Kennedy Ellis 1 drawing blood 2 enlarged spleen 3 polycythemai vera 4 what do you experience? 5 the mutation in which gene causes this blood cancer 6 what does polycythemia cause? increased number of red blood cells helps fight infection and filter unwanted material and gets bigger when there is too much RBCs janus kinase 2 (JAK2) heart attack or stroke itchiness, headches, dizziness, bleeding/bruising, weakness, fatigue helps reduce # of RBCs