METHIMAZOLE DESENSITIZATION IN A 4-YEAR-OLD WITH REFRACTORY GRAVES DISEASE

ABSTRACT Objective The objective is to describe a 4-year-old girl with Graves disease and methimazole allergy who underwent desensitization, allowing continued methimazole use when other treatments were contraindicated. Methods We formulated a desensitization plan utilizing cetirizine and prednisone for a patient with previously-diagnosed Graves disease who developed urticaria and arthralgias from methimazole. She was admitted for monitoring of rash, urticaria, angioedema or anaphylaxis. Her methimazole dose was increased as tolerated and then titrated as an outpatient. Results A 4-year-old girl presented with a heart rate of 195 beats/minute, blood pressure of 145/108 and subsequent labs of undetectable thyroid stimulating hormone (TSH), free T4 5.8 ng/dl, Thyroid peroxidase antibody 11.5 IU/ml, TSH receptor antibody 39.03 IU/L, consistent with Graves disease. She developed urticaria and arthralgias after 2.5 weeks on methimazole, which resolved with drug cessation. Because of her age, the risks of radioactive iodine ablation and surgery were concerning; therefore, methimazole desensitization was attempted. Prednisone (1 mg/kg/day) and cetirizine (5 mg/day) were started prior to low-dose methimazole re-introduction and continued for 7 days. The methimazole was then gradually increased to a final dose of 15 mg daily (0.8 mg/kg/day). Her free T4 normalized within a month (1.12 ng/dl) and her TSH normalized within 10 months (4.61 mcU/ml). Except for two possible breakthrough allergic responses that resolved with pulse steroids, she continues to tolerate methimazole. Conclusion We describe a case of methimazole desensitization. In this patient, pre-treatment with prednisone, coupled with daily cetirizine, successfully induced methimazole tolerance when other treatment modalities were contraindicated.