A 65-year-old man received a diagnosis of idiopathic thrombocytopenic purpura (ITP) 2 years ago based on an isolated thrombocytopenia (55 × 10 3/μL); however, bone marrow showed only increased megakaryocytes, including naked ones (panel A), and cytogenetic studies were unremarkable. The patient failed improvement with steroids, intravenous immunoglobulin, and Rituxan therapy. Also, romiplostim therapy was administered weekly for 4 weeks without improvement. Repeat bone marrow during romiplostim treatment showed hypercellular marrow with 60% to 70% cellularity with increased megakaryocytes and 3/4 reticulin fibrosis (panel B). Repeat marrow was done after the patient was off romiplostim for 6 weeks. The marrow showed progression of the process to a picture of myelodysplastic/myeloproliferative neoplasms (MDS/MPN) with cellularity of 90% with dysplastic megakaryocytes, granulocytosis/myeloid hyperplasia, and 4/4 reticulin fibrosis (panel C). The blood shows leukoerythroblastosis, Pelgeroid polymorphonuclear neutrophils, and blasts (5%) (panel D).We are submitting a case of MDS/MPN, most likely misdiagnosed as ITP, that progressed rapidly after treatment with romiplostim. Transformation of MDS to acute myeloid leukemia in patients treated with romiplostim has been previously reported, but, to the best of our knowledge, there is no report on progressive fibrosis after the discontinuation of romiplostim. Romiplostim should thus be avoided in MDS patients to minimize the risk of progressive fibrosis or the development of an MDS/MPN-like condition.