Arsenic trioxide has been shown to be effective and approved by the US Food and Drug Administration in treating patients with relapsed acute promyelocytic leukemia (APL). 1,2 The dermatologic side effects of arsenic trioxide such as pruritus and dermatitis are usually mild and self-limiting. We report a case of severe radiation recall dermatitis in a patient with APL treated with arsenic trioxide.This patient was a 49-year-old African-American female when she was diagnosed with stage IIb left breast cancer in 1999 treated with modified radial mastectomy. After surgery, she received adjuvant chemotherapy with four cycles of adriamycin/cyclophosphamide and four cycles of paclitaxel, followed by adjuvant radiation to the left chest wall, left supraclavicular and left internal mammary nodes, 5000 cGy in 25 daily fractions, and tamoxifen. She had done extremely well until September 2001 when her white blood cell (WBC) decreased to 3700/ml, Hgb to 9.9 g/dl with MCV being 100.6 fl, and platelet count 220 000/ml. When she was referred to this institution in February 2002, the WBC was 1500/ml. Serum haptoglobin was 182 mg/dl, serum iron 140 mg/dl, TIBC 236 mg/dl, vitamin B 12 level 489 pg/ml (normal 210-705), RBC folate level 760 ng/ml (normal 4164). Bone marrow examination revealed 80% cellularity and 68% promyelocytes and blasts with prominent Auer rods consistent with APL. The diagnosis was confirmed by cytogenetic study and florescence in situ hybridization of the bone marrow showing 46,XX,t(15;17)(q22;q21) [20]. She was treated with all-trans-retinoic acid (ATRA) 45 mg/m 2 /day, daunorubicin 50 mg/m 2 /day days 3-6, and cytarabine 200 mg/m 2 /day continuous infusion days 3-9 with complete morphologic and molecular remission achieved in 5 weeks. Intravenous dexrazoxane 500 mg/m 2 was also added because her left ventricular ejection fraction was only 44% probably secondary to prior Adriamycin and chest wall radiation. She then received consolidation therapy consisting of arsenic trioxide 0.15 mg/kg/day for 5 days each week for 5 weeks, repeat once after 2 weeks of rest. By day 2 at week 3 of the second cycle of arsenic trioxide, she started noticing skin peeling off her feet and hands. In addition, she also noticed hyperpigmentation, vesicular formation and superficial desquamation of the left chest wall, well demarcated to her previous radiation field (Figure 1). In view of a possible radiation recall reaction, arsenic trioxide was discontinued. No systemic antibiotic was prescribed because cellulitis was unlikely with such a well-defined margin. The skin lesions were treated with topical triamcinolone/ silver sulfadiazine cream with good response. She proceeded with further consolidation of ATRA and daunorubicin/dexrazoxane without further problem. She is currently on maintenance ATRA and in continuous remission 1 year after diagnosis.Radiation recall is an inflammatory reaction at a previously irradiated fields usually associated but not limited to cytotoxic drugs. The common inciting agents (complete list of refer...