MPL and Thrombocytopenia: Severe thrombocytopenia of patients with CAMT and patients with THPO mutations provides the most convincing evidence that the THPO/MPL pathway is essential for thrombopoiesis.6,20 THPO-RAs have been used as a critical treatment for thrombocytopenia.4 However, some patients with thrombocytopenia do not respond to treatment with THPO-RAs.5 Available treatments for patients with CAMT include platelet transfusion and HSCT, but not THPO-RA due to MPL mutations.