JAK2 and anemia (phenotype): Other side effects of JAKi include cytopenias, anemias, and thrombocytopenia, as well as the potential for malignancy (Ghoreschi et al., 2011).This risk is thought to be due to JAK2 specific inhibition, as the cytokine receptors for erythropoietin and thrombopoietin signal through JAK2.