LETTERSprednisone, new skin lesions and tense bilateral knee effusions were noted; bilateral knee corticosteroid injections were given and Dapsone was restarted (100 mglday). On November 18, 1983 she developed severe epigastric pain which prompted another admission. She had new bullous lesions around the elbows, was in diabetic ketoacidosis, and her abdomen was tender. When abdominal radiographs demonstrated free air under the diaphragm, surgical exploration revealed a perforated duodenal ulcer. She recovered uneventfully, receiving parenteral corticosteroids to an equivalent of 120 mg of prednisone initially, and was discharged 10 days later receiving 60 mg/day of prednisone as well as insulin to control her diabetes. She received no Dapsone during this hospitalization.On December 4, 1983 she was readmitted because of a worsening skin condition and development of new joint pain 2 days before, for which Dapsone (100 mg/day) and Plaquenil (200 mg twice a day) had been started. Soon thereafter, she developed new skin lesions. She also presented some behavioral changes which could not be related to hypoglycemia. The diagnosis of central nervous system lupus was considered, but her neurologic evaluation results were normal as were an electroencephalogram and a lumbar puncture. Prednisone was continued at the same dose, but Plaquenil and Dapsone were discontinued since it was impossible to determine if the behavioral changes were in any way related to either of these medications. Two days later Dapsone was restarted. She rcceived 1 dose that evening; by midnight she had severe itching, erythema, and bullae around her elbows, forearms, and knees. She received her next dose of Dapsone the following morning and by midday had more skin lesions. Dapsone was discontinued and prednisone was maintained at the same dosage. Over the next few days the skin lesions rapidly cleared. She was discharged 3 days later with marked improvement of her skin. As of now, her prednisone dosage has been tapered to 45 mg/day, and she has remained free of new skin lesions.Although during the first 2 instances it was not completely clear that the worsening of the skin lesions was related to the use of Dapsone, during the third attemptwhile she was in the hospital-the relationship between its use and the worsening of her skin lesions was unquestionable. A very severe dermatitis which can be bullous in nature has been described as a possible side effect of this sulfa derivative product (Dapsone, Physician's Desk Reference. Thirty-seventh edition. Oradell, NJ, Medical Economics Co., 1983, pp 1021-1022). Therefore, we want to call the attention of the practicing rheumatologist to this side effect which can be mistaken as a failure to respond to the initial dose.