Development of Sweet's syndrome during all-trans retinoic acid therapy for acute promyelocytic leukemia

A 54-year-old woman visited our hospital because of gingival bleeding on May 31, 1998. After hematological and bone marrow examinations, she was diagnosed as having acute promyelocytic leukemia (APL) and given all-trans retinoic acid (ATRA) therapy starting on June 1. Anti-cancer drugs were administered for 5 days from June 12 because of an increase in the number of APL cells. The patient developed fever on June 20, and nodular erythematous eruptions appeared on June 23. Sweet's syndrome was diagnosed from biopsy samples of the eruption. ATRA was therefore discontinued, and prednisolone was started on June 29. The fever and skin eruptions improved rapidly, and complete remission was obtained on July 13. Sweet's syndrome due to ATRA may be a partial form of retinoic acid syndrome, in which the differentiated leukemic neutrophils increase and invade various organs. However, Sweet's syndrome must be considered regardless of the WBC count because in this case the syndrome occurred even when the WBC count was not high.