[Drug eruption (erythema multiforme type) following chemoradiotherapy with mitomycin C and 5-fluorouracil administration for squamous cell carcinoma of the anal canal].

We report a case of drug eruption (erythema multiforme type) in a 54-year-old woman, following concurrent chemoradiotherapy for squamous cell carcinoma of the anal canal. Chemotherapy comprised one cycle of mitomycin C 10 mg/m2/day (intravenous bolus injection)on day 1 and 5-fluorouracil(5-FU)1, 000 mg/m 2/day (continuous intravenous infusion) on days 1-4 of radiotherapy. External irradiation of the pelvic space was performed, using daily fractions of 1. 5 Gy(total dose, 33 Gy). From day 4 after chemoradiotherapy, erythema appeared proximal to the forearm site used for drug administration. On day 6, erythema was noted on the trunk, hip and thigh. We suspected erythema multiforme based on the appearance of wheals and target lesions of the skin and a patient history of chemoradiotherapy. Steroids were administered orally, which resolved systemic eruption at week 2. The patient also experienced grade 3 leukocytopenia, neutropenia, thrombopenia, diarrhea, and anorexia. Although we could not provide sufficient chemotherapy and radiation therapy due to severe side effects, squamous cell carcinoma of the anal canal responded extremely well with a marked decrease in complete response. We surmise that the drug eruption was associated with 5-FU. Concurrent chemoradiotherapy is safe and effective for squamous cell carcinoma of the anal canal, but care is required to prevent drug eruption during treatment.