Review Question - QID 213344

A 35-year-old man presents to the clinic complaining of skin lesions on his hands and face. The lesions started appearing after his vacation to Hawaii where he snorkeled, hiked, and sunbathed on the beach. He complains of itchiness and moderate pain around the skin lesions but denies fever, weight changes, headaches, mental status changes, abdominal pain, or bowel changes. His past medical history is significant for asthma and allergic rhinitis, both of which are well controlled with medications. A physical examination demonstrates skin blisters and hyperpigmentation concentrated on the hands and face (shown in Figure A). What enzyme is likely deficient in this patient?