A 45-year-old man presents to the office for evaluation of a blistering skin rash. He was out in the sun with his family at a baseball game several days ago. Later that evening, he developed a severe blistering rash on the forearms, hands, neck, and legs. He has tried over-the-counter topical emollients but to little effect. The patient has had similar rashes in the past that eventually self-resolved. The first of such episodes occurred around 10-years ago. Past medical history is also significant for hyperlipidemia and chronic hepatitis C virus infection. He does not consume alcohol, tobacco, or illicit substances. Vitals are within normal limits. Physical examination reveals small ruptured blisters diffusely across the forearms, hands, neck, and lower legs. A defect in which of the following steps of the heme biosynthesis pathway is most likely responsible for this patient’s symptoms?

Porphyria cutanea tarda

Foundational SciencesPathologyBlood and lymphoreticular systemAnemia, cytopenias, and polycythemia anemiasHeme synthesis disorders

Organ SystemsBlood and lymphoreticular systemPathologyAnemia, cytopenias, and polycythemia anemiasHeme synthesis disorders

Definitions & Key takeaways

Porphyria cutanea tarda is a rare metabolic disorder that is caused by an abnormality in the enzyme uroporphyrinogen decarboxylase. Symptoms of this disorder usually involve the skin, as it can lead to blisters and skin discoloration. Treatment for this disorder usually involves medications such as hydroxychloroquine and phlebotomy, as well as lifestyle changes such as avoiding alcohol.

Porphyria cutanea tarda

Definitions & Key takeaways

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