Other pathogenic MPNmutations in calreticulin (CALR) and thrombopoietin receptor (MPL)genes also cause MPN by activating JAK2 signaling.6,7 Inaddition, mutations in JAK2 have been linked to other hematologicmalignancies, such as acute lymphoblastic leukemia, acute myeloidleukemia, and acute megakaryoblastic leukemia.8−10. The gene discussed is CALR; the disease is acute megakaryoblastic leukemia.