Sweet's syndrome followed by retinoic acid syndrome during the treatment of acute promyelocytic leukemia with all-trans retinoic acid.

We present here the case of a 49-year-old female with acute promyelocytic leukemia (APL) who, after first developing all-trans retinoic acid (ATRA)-related Sweet's syndrome, was later diagnosed as having retinoic acid (RA) syndrome. Preceding the RA syndrome diagnosis, she developed a fever as well as erythematous nodules on her upper arms. These symptoms were observed on day 18 of treatment with ATRA. Ten days later, she began to develop respiratory distress. There was no indication of infection, and her condition did not improve with empiric therapy. At this time, the diagnosis of RA syndrome was made, resulting in the initiation of steroid pulse therapy, and within 24 hours her elevated fever and respiratory distress improved markedly. In addition, the erythematous nodules gradually began disappearing. A skin biopsy revealed a dense dermal infiltrate consisting of neutrophils.