Discoid Lupus Erythematosus Exacerbated by Contact Dermatitis Caused by Use of Squaric Acid Dibutylester for Topical Immunotherapy in a Patient with Alopecia Areata

A 57-year-old Japanese male with an 18-year history of discoid lupus erythematosus (DLE) developed alopecia areata and was treated with topical immunotherapy using squaric acid dibutylester (SADBE). After initial sensitization with 2% SADBE and subsequent low-concentration re-exposure to induce contact dermatitis on the scalp, the patient developed multiple red scaly lesions on his scalp and face within 2 months. These lesions were diagnosed as DLE, indicating that the contact dermatitis exacerbated his DLE. This case highlighted that DLE can be exacerbated by contact dermatitis, a rare occurrence with only two previously reported cases.