Late-onset immune thrombocytopenia after unrelated cord blood transplantation for chronic myelomonocytic leukemia.

Several reports have been published on autoimmune hematologic complications, including immune thrombocytopenia (ITP), after cord blood transplantation (CBT). However, there have been no reports of late-onset ITP following CBT. A 51-year-old male with chronic myelomonocytic leukemia received unrelated CBT in 2012. During regular follow-up visits every 3-6 months, his complete blood count remained normal until March 2024. In September 2024, 12 years after the CBT, the patient suddenly developed severe thrombocytopenia. Following a diagnosis of ITP, the patient was treated with intravenous immunoglobulins and prednisone. With follow-up period of 5 months after the onset of ITP, the patient is still alive with a platelet count of 126 × 10⁹/L. This case suggests that late-onset ITP after CBT occurred suddenly and may be life-threatening. Long-term follow-ups and regular clinic visits may reduce the risk of delays in diagnosis and treatment.