Agranulocytosis due to secondary exposure to antithyroid drugs in a relapsed Graves' disease patient

Antithyroid drugs are the most common treatment modality for Graves' disease and are used for the treatment of relapsed Graves' disease in Korea. Agranulocytosis is a rare and severe complication of antithyroid drug therapy, and most cases occur within 3 month after drug treatment. Agranulocytosis can develop in patients who have relapsed Graves' disease and undergo a second course of antithyroid drugs with a prior uneventful course of drug therapy. We report a case of antithyroid drug-induced agranulocytosis in a relapsed Graves' disease patient who had undergone prior uneventful antithyroid drug therapy. We also present a review of the relevant literature.