A 52-year-old man with Fitzpatrick type V skin presented for evaluation of a photodistributed eruption of unknown origin. The patient reported a 20-year history of the dermatitis, with worsening severity during the past 6 years. He had required one hospital admission with intravenous methylprednisolone and two extended courses of oral prednisone (starting dose of 60 mg/d). He complained of pruritus and swelling localized to the sun-exposed areas of the forearms, face, and neck, with notable sparing of photoprotected areas of his skin. He denied new medications, and a systemic review of systems was noncontributory.