Abstract
A 51-year-old Caucasian male developed Graves' thyrotoxicosis following long-standing treatment for hypothyroidism. After a short period of treatment with carbimazole, he developed agranulocytosis and required total thyroidectomy. In this relevant case report, we review several pathogenetic mechanisms that explain the transformation of autoimmune hypothyroidism into Graves' disease and the possible approaches to the management of agranulocytosis secondary to antithyroid medications. Further studies are required to determine the best way to manage severe thyrotoxicosis when agranulocytosis develops due to antithyroid medications.