[Agranulocytosis/granulocytopenia after long-term use of thiamazole]

Agranulocytosis/granulocytopenia is a rare side effect of thyreostatics. Earlier publications state that for thiamazole this side effect occurs during the first few months of treatment. In two patients this thiamazole-induced agranulocytosis/granulocytopenia only occurred after years of treatment. A 53-year-old man presented with fever after a visit to Suriname. He had used thiamazole for 12 years for Graves' hyperthyroidism. The second patient, a 31-year-old woman, presented at the emergency department with fever and sore throat after 13 years of intermittent treatment with thiamazole. Both patients had an agranulocytosis/granulocytopenia and leukopenia. This was thought to be a side effect of thiamazole and blood values normalised after cessation of therapy. Both patients were treated empirically with broad-spectrum antibiotics during the agranylocytic period. They then received radioactive sodium iodide. To our knowledge this case report is the first to describe agranulocytosis/granulocytopenia following long-term treatment with thiamazole.