Sertraline- and Mirtazapine-Induced Severe Neutropenia

Ms. A, a 44-year-old woman with complaints of sleep disturbance, lack of energy, and unhappiness, was diagnosed with major depressive disorder and administered mirtazapine, 30 mg/day. Her medical history was negative, and the results of routine blood tests (WBC count of 6.8×10⁹/liter) were unremarkable except for a total cholesterol level of 204 mg/dl. Three weeks later, she came in with complaints of a severe sore throat, difficulty swallowing, a loss of appetite, and an aphthous ulcer in her oral mucosa, with a slightly elevated body temperature of 37.7°C during her physical examination. In subsequent blood counts, neutropenia (a WBC count of 2.2×10⁹/liter) was detected, and a blood smear revealed a granulocyte number of 1.1×10⁹/liter. Mirtazapine was immediately discontinued, and sultamicillin, 375 mg b.i.d., was started after consulting with the otorhinolaryngology department. Within 2 weeks, Ms. A’s WBC count and granulocyte count had gradually increased to 3.8×10⁹/liter and 3.2×10⁹/liter, respectively. Four weeks after discontinuation of mirtazapine, sertraline was administered at 50 mg/day. Within 6 weeks, Ms. A’s depression had responded to treatment, with more than a 50% reduction of her score on the Hamilton Depression Rating Scale, while her WBC count was 6.1×10⁹/liter. Upon her final assessment, after 6 months of taking sertraline, her depression had remitted completely, without any adverse effects.