 Ineffective platelet production has been proven to play a role in the etiology of Immune Thrombocytopenia ITP in addition to increased platelet destruction. The second-generation thrombopoietin TPO mimetics have shown good efficacy in boosting platelet counts in the great majority of patients with chronic ITP in several clinical trials.1, 2 Nevertheless, about 20 of patients with ITP fail to respond to the TPO mimetic treatment. Those treatment-resistant patients are un-characterized and the reasons for the lack of response have not been studied. The identification of predictive blood biomarkers of patients response to treatment will be useful in reducing both cost and potential side effects; and it will be of equal importance and interest to investigate the molecular mechanisms underlying the patients heterogeneous responses to TPO mimetic treatment. 