Development of myelofibrosis during eltrombopag treatment in a patient with immune thrombocytopenia.

Eltrombopag, a thrombopoietin (TPO) receptor agonist, is effective for treating refractory immune thrombocytopenia (ITP). However, the development of bone marrow fibrosis is a concern. A 78-year-old man was diagnosed with ITP in 2004. His platelet count did not increase after eltrombopag treatment initiation in 2014. However, anemia progressed, along with the presence of immature myelocytes, erythroblasts, and tear drop cells. At 8 months after initiating eltrombopag treatment, the patient underwent a bone marrow biopsy that showed grade 2 myelofibrosis. Hence, eltrombopag was discontinued. In our experience with this case indicates that careful observation is required while using TPO receptor agonists.