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 a long history of discoid lupus erythematosus (DLE) developed alopecia areata and was treated with topical squaric acid dibutylester (SADBE). After initial sensitization and subsequent low-concentration re-exposure to SADBE, he developed multiple red scaly lesions on his scalp and face, which were diagnosed as exacerbated DLE. This case highlighted that DLE can be worsened by contact dermatitis, a rare occurrence with only two previously reported cases.