ABSTRACT
Agranulocytosis is a rare but the most serious life-threatening complication of antithyroid drug therapy. Most cases of agranulocytosis occur within the first 3 months of antithyroid drug therapy, but some cases happen several years after starting treatment. However, there is a paucity of data on the delayed onset of agranulocytosis. We report a case of methimazole-induced agranulocytosis with suppurative pharyngotonsillitis occurring during the long-term treatment. A 48-year-old woman with Graves' disease visited our hospital with sore throat and high fever (39.2degrees C). She had continuously been treated with methimazole for the preceding 7 years-15 to 40 mg daily from Jul 2007 until Apr 2014 and 50 mg daily from May 2014 until September 2014. A month ago, the dose of methimazole had been reduced to 10 mg daily due to transient neutropenia. Her initial blood tests showed an absolute neutrophil count of 40/microL. Moreover, physical examination showed right neck enlargement. We stopped methimazole, and she was empirically treated with broad-spectrum antibiotics and granulocyte colony stimulating factor. Neck CT scan detected enlarged right tonsils and lymph node. Cervical lymph node biopsy only showed acute and chronic inflammation. About 3 weeks after she recovered, 10 mCi of radioiodine ablation therapy was performed. This case suggests that the sign of agranulocytosis should be carefully monitored in patients with Graves' disease, throughout the course of treatment with methimazole, even under the long-term therapy.