Two Cases of Methimazole-Induced Agranulocytosis With Their Risk Factors

Aye Khine; Kiranjit Dhillon; Linda Jo; Vanessa Wormser; Soe Naing; Shreela Mishra

doi:10.1016/j.aace.2021.10.005

Two Cases of Methimazole-Induced Agranulocytosis With Their Risk Factors

AACE Clin Case Rep. 2021 Nov 3;8(2):82-84. doi: 10.1016/j.aace.2021.10.005. eCollection 2022 Mar-Apr.

Authors

Aye Khine¹, Kiranjit Dhillon¹, Linda Jo¹, Vanessa Wormser¹, Soe Naing², Shreela Mishra²

Affiliations

¹ Department of Internal Medicine, University of California San Francisco-Fresno, Fresno, California.
² Department of Medicine, Division of Endocrinology, University of California San Francisco-Fresno, Fresno, California.

Abstract

Background: Antithyroid drugs, such as methimazole (MMI), are standard therapies for the medical management of thyrotoxicosis. Agranulocytosis is a rare but lethal adverse effect of antithyroid medications. We have reported 2 cases of MMI-induced agranulocytosis with similar risk factors that likely predisposed them to this adverse reaction.

Case report: Case 1 involved a 71-year-old woman, with a history of Graves disease, who presented with an altered mental status. She was recently discharged on 40 mg of MMI twice daily, and she continued this dose for 2 months. She was readmitted and found to have neutropenic fever in the setting of MMI-induced agranulocytosis. MMI was discontinued, and she was started on filgrastim. Her cell counts gradually improved, and she was subsequently discharged.Case 2 involved a 68-year-old woman, with a history of Graves disease, who presented with severe back pain, nausea, and vomiting. She was recently discharged on 10 mg of MMI twice daily, which was increased to 10 mg 3 times a day. She was readmitted to the hospital because of a septic shock in the setting of pneumonia, colitis, bacteremia, and MMI-induced agranulocytosis. A bone marrow biopsy showed a polyclonal infiltrate with up to 85% plasma cells. Despite treatment with antibiotics, filgrastim, and continuous renal replacement therapy, she ultimately passed away.

Discussion: Although these cases had differing outcomes, they shared similar features and risk factors, including older age, female sex, and relatively higher doses of MMI.

Conclusion: Close follow up and awareness of risk factors, such as age, female sex, and higher doses of MMI, may decrease the risk of MMI-induced agranulocytosis and fatal outcomes.

Keywords: ANC, absolute neutrophil count; Hgb, hemoglobin; MMI, methimazole; MMI-AGRAN, MMI-induced agranulocytosis; Plt, platelet; T3, triiodothyronine; T4, thyroxine; TSH, thyroid-stimulating hormone; WBC, white blood count; agranulocytosis; antithyroid; hyperthyroidism; methimazole.

Publication types

Case Reports