SAT-600 Relapse of Agranulocytosis after Recovery of Methimazole-Induced Agranulocytosis

Background: Agranulocytosis is the most feared side effect of antithyroid-drug therapy. In the largest series, agranulocytosis occurred in 0.35 percent receiving methimazole. The causative antithyroid-drug should be stopped and treatment includes broad-spectrum antibiotics and granulocyte-colony stimulation factor may be needed in selected patients(1). Here, we report a case of agranulocytosis relapse after the recovery of methimazole-induced agranulocytosis. Case: A 35-year-old woman was admitted to hospital by fever lasted 3 days. The patient was diagnosed hyperthyroidism 3 weeks ago, and she was taking methimazole 15mg daily. Lab finding of admission day was 370/mm(3) of granulocyte count, normal C-reactive protein, 4.64ng/mL of T3, 7.66ng/dL of free T4, below 0.05uIU/dL of Thyroid-stimulating hormone. After isolated admission care including methimazole stop and follow-up of 3 days, granulocyte count was elevated to 1,190/mm(3). The patient was discharged without restarting other antithyroid-drugs. 4 days later, the patient admitted again by fever and sore throat. The granulocyte count was 10/mm(3) with normal range of C-reactive protein, above 6.51ng/mL of T3, above 7.77ng/dL of free T4, below 0.05uIU/dL of Thyroid-stimulating hormone. We used granulocyte-colony stimulation factor and intravenous cefepime. After 4 days, granulocyte count improved to 1,610/mm(3) and fever was subsided. After recovery, total thyroidectomy was performed for hyperthyroidism. The patient is now taking levothyroxine in the outpatient clinic without further additional agranulocytosis episodes. Conclusion: We are reporting a relapse of agranulocytosis after recovery of methimazole-induced agranulocytosis. Even if the antithyroid-drug is not used again after the recovery of agranulocytosis, attention to relapse of agranulocytosis and education of the patient may be necessary. Reference: 1. David S. Cooper, M.D. (March 3, 2005). “Antithyroid drugs" New England Journal of Medicine 2005; 352:905-917