Graves Disease Following Subacute Thyroiditis in a Chinese Man.

The development of Graves disease (GD) after subacute thyroiditis (SAT) is rare, with approximately 31 reported cases, of which only 5 occurred in men. We describe a case of GD diagnosed based on newly elevated thyroid-stimulating immunoglobulin (TSI) and thyroid-stimulating hormone (TSH) receptor autoantibody (TRAb) levels after SAT. A 32-year-old Chinese man presented with right anterior neck pain, swelling, sore throat, cough, and fever. He had a diffuse tender goiter but no proptosis, lid lag, or stare. His TSH level was 0.03 mIU/mL (normal range [NR] 0.45-5.33 mIU/mL), serum free thyroxine (FT4) level was 2.40 ng/dL (NR 0.61-1.44 ng/dL), total triiodothyronine (TT3) level was 113 ng/dL (NR 87-178 ng/dL), TSI level was <0.10 IU/L (NR < 0.10 IU/L), and erythrocyte sedimentation rate was 21 mm/h (NR < 15 mm/h). After 7 weeks of prednisone, the symptoms resolved, FT4 level was 0.95 ng/dL, and TT3 level was 91 ng/dL. At 11 weeks after SAT onset, the TSH level was <0.01 mIU/mL, TT3 level was 257 ng/dL, FT4 level was 3.03 ng/dL, TSI level was 1.94 IU/L, then 3.42 IU/L 2 weeks later, TRAb level was 8.72 IU/L (NR < 2 IU/L), and erythrocyte sedimentation rate was 4 mm/h. After 1 month of methimazole, the FT4 level was 1.32 ng/dL and TT3 level was 110 ng/dL. Genetic testing revealed human leukocyte antigen-B35 and DRB1∗15:01 positivity. GD after SAT is thought to be due to the activation of thyroid autoimmunity induced by SAT in genetically susceptible individuals. This case illustrates the induction of thyroid autoimmunity after SAT, resulting in GD, supporting TSI and/or TRAb testing if hyperthyroidism recurs. The presence of HLA alleles associated with SAT and GD suggests a genetic contribution to the development of thyroid autoimmunity.