Acute myeloid leukemia developing secondary immune thrombocytopenia after umbilical cord blood transplantation

A 64-year-old man was diagnosed with acute myeloid leukemia M2 (FLT3-ITD-positive). After induction chemotherapy and four courses of consolidation therapy, he underwent umbilical cord blood transplantation (CBT) in his first remission. He developed acute graft-versus-host disease (skin stage 2) after successful engraftment. On post-transplantation day 147, he was admitted to the hospital suffering from pneumonia. During the treatment, drastic thrombocytopenia was observed on day 251. Both platelet-associated immunoglobulin G and platelet antibody producing B cells were detected, and he was diagnosed with immune thrombocytopenia (ITP). Treatment with prednisolone (1 mg/kg/day), eltrombopag (25 mg/day), and intravenous immunoglobulin (400 mg/kg) was commenced, but there was no improvement in his platelet count. After switching from eltrombopag to romiplostim (350 µg/week), and addition of cyclosporine, the platelet count rapidly elevated to 150,000/µl. ITP after allogenic stem cell transplantation is a rare complication, and it is often refractory to the 1st-line treatment such as steroids. Herein, we report successful treatment using a combination of romiplostim and an immunosuppressive agent in the case of treatment failure in ITP that developed after CBT.