Derm Dx: Photosensitive blisters on the hands

A patient, aged 65 years, presented with complaints of blisters on his hands and arms for several weeks. He reported that he thought the blisters were made worse by the sun.

The patient was recently started on metformin for diabetes and naproxen for arthritis. His urine porphyrin levels were normal. A complete exam of the skin and ...