[Antithyroid drug-induced agranulocytosis: special reference to normal white blood cell count agranulocytosis]

This retrospective study was aimed at establishing the importance of the leukocyte differentiated count and not only routine white blood cell count in patients treated with antithyroid drug. From 1975 to September 1992, 77 patients with antithyroid drug-induced agranulocytosis were examined. In 12 patients (15.6%), the total white blood cell (WBC) count was greater than 3000/mm3. Eight of them showed a downward trend in their leukocyte counts (3000-4000/mm3). Consequently, granulocyte counts were measured. Two of the 12 patients had "symptomatic" agranulocytosis detected after the occurrence of infection. Because antithyroid drug-induced agranulocytosis was strongly suspected, granulocyte counts were checked. In the remaining two patients, the total WBC count was 5700/mm3 and 5900/mm3, respectively. One was hospitalized to receive thyroid surgery. Although she was asymptomatic, agranulocytosis was unexpectedly detected on a routine preoperative examination. The other was diagnosed as agranulocytosis by routine WBC and granulocyte count monitoring since June 1989. Correct diagnosis was based on the leukocyte differentiated counts. We concluded that the leukocyte differentiated count and not only routine white blood count was critically important for the correct diagnosis of antithyroid drug-induced agranulocytosis in patients with Graves' disease.