OBJECTIVE

To describe a case of agranulocytosis and severe hepatotoxicity associated with carbimazole treatment.

CASE SUMMARY

A 37-year-old woman was diagnosed with severe hyperthyroidism resulting from Graves' disease. Treatment with carbimazole 30 mg/day was initiated. Within 15 days following the start of therapy, both minor (eg, pruritus, rash, urticaria, fever, arthralgias) and potentially life-threatening (eg, agranulocytosis, severe mixed hepatotoxicity with severe cholestatic jaundice) adverse effects developed. The patient's symptoms and laboratory abnormalities resolved following withdrawal of carbimazole. Treatment with other antithyroid drugs was not attempted, and (131)I ablation of the thyroid was successfully performed. Thyroid function was maintained with standard follow-up care. Agranulocytosis, identified following bone marrow biopsy, was treated with granulocyte colony-stimulating factor.

DISCUSSION

Agranulocytosis and hepatotoxicity are rare adverse effects associated with carbimazole treatment and are usually dose- and age-related. The likelihood that carbimazole induced these undesirable events in our patient is rated as probable based on the Naranjo probability scale. We believe this case to be the first to describe minor and major adverse effects related to carbimazole therapy in a patient with Graves' disease.

CONCLUSIONS

Major adverse effects associated with carbimazole are infrequent. However, clinicians need to be aware that the effects described here, including severe liver failure and bone marrow toxicity, may occur in patients receiving this drug.