We report an unusual case of a patient who was cured of one autoimmune disease (palmoplantar pustular psoriasis (PPP)) but developed another autoimmune disease (autoimmune thyroiditis) after allogeneic BMT. A 40-year-old man suffering from AML with PPP underwent allogeneic BMT from his HLA-identical sister for the treatment of AML. The patient experienced complete clearance of the cutaneous PPP despite the cessation of immunosuppressive therapy for over 2 years. However, he developed hyperthyroidism with anti-thyroglobulin antibodies 5 months after BMT, although he had showed normal thyroid functions without anti-thyroglobulin antibodies before BMT. The donor had no history of thyroid diseases and showed normal thyroid functions but was positive for anti-thyroglobulin antibodies. Thus, even when the donor is in a subclinical state, autoimmune thyroiditis may be transferred from donors to recipients by BMT.