A nurse is caring for a client who has a new prescription for methimazole for hyperthyroidism. Which of the following findings should the nurse report to the provider as a potentially life-threatening adverse effect?

A. A sore throat in a client taking methimazole could indicate a serious neutropenic reaction, which is a potentially life-threatening side effect of this medication. B. A WBC count of 12,000/mm³ is slightly elevated but not immediately life-threatening and is unlikely to be related to methimazole. C. Insomnia is a common symptom of hyperthyroidism and not an adverse effect of methimazole. D. Weight loss is expected with hyperthyroidism and does not warrant immediate concern unless it is severe or worsening.