Agranulocytosis: a rare complication of the thionamides

Abstract Agranulocytosis is a rare and life-threatening side effect of antithyroid drugs (ATD); it has been reported in < 0.2% of patients, usually within the first 3 months after starting ATD. We present a 62-year-old Libyan female patient who developed agranulocytosis 3 months after starting treatment with methimazole for hyperthyroidism. After 1 month of doubling her ATD dose, she developed a fever, sore throat, and generalized weakness for several days. Laboratory examinations revealed agranulocytosis (total leukocyte count was 1.14 × 103/µL, with granulocytes at 2.99% and lymphocytes at 93.21%). She was hospitalized, ATD was discontinued, and empirical antibiotic treatment was given. She was started on granulocyte colony-stimulating factor. Her cell counts improved, and she was discharged. The present case report aims to increase awareness of this potentially lethal adverse effect of ATD treatment. Patient education and close monitoring of high-risk patients are the key to reduce its morbidity and mortality