Romiplostim-associated increase in CD34+ megakaryocytes in a case of immune thrombocytopenia: A case report

We report a patient with chronic immune thrombocytopenia purpura who underwent bone marrow biopsies before and after treatment with romiplostim. The biopsy after treatment with romiplostim showed a marked increase in the numbers of megakaryocytes which were CD34 positive. Because increased numbers of CD34 positive megakaryocytes are a feature of myelodysplastic syndromes, an extensive evaluation for myelodysplasia was undertaken including cytogenetic studies, myelodysplasia FISH studies, and NGS studies for mutations associated with myelodysplasia, as well as morphologic evaluation. There was no evidence for myelodysplasia. We suggest that treatment with romiplostim caused the increased number of CD34 positive megakaryocytes in this patient. We propose that the mechanism is through romiplostim mediated cell signaling for endomitosis. DNA synthesis including endomitosis is associated with CD34 expression on megakaryocytes.