Morning granulocytopenia in a case of Graves' disease

A 65-year-old woman with Graves' disease presented marked diurnal changes in white blood cell (WBC) and granulocyte counts. Granulocyte count was low and sometimes decreased to 0.2-0.3 x 10(9)/l in the early morning and increased in the afternoon irrespective of her thyroid status. She did not develop sore throat or fever during the investigation period. The present study indicates that these unusual diurnal changes in WBC and granulocyte counts should be considered in the differential diagnosis of agranulocytosis in Graves' disease patients treated with an antithyroid drug.