Acute thyrotoxicosis-like graft-versus-host disease after cord blood transplantation

Reports of thyrotoxicosis and hypothyroidism occurring immediately after allogeneic stem cell transplantation are limited, and the detailed mechanisms remain unclear. Here, we present the case of a man in his 20s with thyrotoxicosis and hypothyroidism that occurred early after cord blood transplantation (CBT), with histopathology suggesting an immune reaction in the thyroid gland. The patient had acute myeloid leukemia and underwent a second CBT procedure. The patient developed thyrotoxicosis on day 43. The patient’s condition initially improved with increasing immunosuppressive drug doses; however, he later developed hypothyroidism and required thyroid hormone replacement therapy. Since conventional subacute thyroiditis, Graves’ disease, and Hashimoto’s thyroiditis were excluded due to the lack of histological evidence and autoantibodies, acute graft-versus-host disease (GVHD) was considered the main cause of thyroiditis. The possibility of even minor post-transplant thyroid function abnormalities is more common than expected and further studies are required.