Supplementary Material for: Methimazole induced agranulocytosis - A clinical case report

Antithyroid drugs are generally safe. However, rare but life-threatening side effects, such as agranulocytosis, may occur.
We present the case of a 70-year-old woman with subclinical hyperthyroidism, previously treated with propylthiouracil which was discontinued due to an unspecified mild white blood cell alteration. On presentation to our clinic, she reported anxiety with no other symptoms and a low dose methimazole (2.5mg/daily) was started. After two months, her white blood cell count was decreased. Methimazole was suspended pending further testing. Six days later, she presented to the emergency room with pharyngitis and fever. Broad-spectrum antibiotics were started and granulocyte-colony stimulating factor was administered following a diagnosis of methimazole induced agranulocytosis.
The onset of agranulocytosis is sudden, and patients should be educated about warning signs. If granulocytopenia is confirmed, medication should be discontinued. Switching to another antithyroid drug is not recommended, because a cross-reactivity between propylthiouracil and methimazole has been observed.

抗甲状腺药物（antithyroid drugs）整体安全性良好，但偶可发生罕见却可致命的不良反应，例如粒细胞缺乏症（agranulocytosis）。
本文报告1例70岁亚临床甲状腺功能亢进症（subclinical hyperthyroidism）女性患者，既往曾接受丙硫氧嘧啶（propylthiouracil）治疗，后因未明确的轻度白细胞异常（white blood cell alteration）停药。患者就诊于我科时仅表现为焦虑，无其他不适，遂予低剂量甲巯咪唑（methimazole，2.5mg/日）治疗。治疗2个月后，患者白细胞计数下降，遂暂停甲巯咪唑并完善进一步检查。6日后，患者因咽炎伴发热就诊于急诊，予广谱抗生素治疗；结合甲巯咪唑诱导粒细胞缺乏症的诊断，予粒细胞集落刺激因子（granulocyte-colony stimulating factor）治疗。
粒细胞缺乏症起病突然，需对患者进行警示症状的健康教育。若确诊粒细胞减少症（granulocytopenia），应立即停用相关抗甲状腺药物。不推荐换用其他抗甲状腺药物，因已有研究显示丙硫氧嘧啶与甲巯咪唑之间存在交叉反应性（cross-reactivity）。