A patient with blistering photosensitivity, hypertrichosis, hyperpigmentation, and friable skin presents in their 40s. Urine fluoresces pink-orange under Wood's lamp. Liver biopsy shows iron overload. Uroporphyrinogen decarboxylase (UROD) activity is markedly reduced. What is the most likely diagnosis, and what is the first-line treatment?

• A Erythropoietic protoporphyria; first-line treatment is beta-carotene and afamelanotide
• B Congenital erythropoietic porphyria; first-line treatment is bone marrow transplantation
• C Porphyria cutanea tarda (PCT); first-line treatment is phlebotomy (to reduce hepatic iron, which inhibits residual UROD) or low-dose hydroxychloroquine ✓
• D Hereditary coproporphyria; first-line treatment is hematin infusion during attacks

Explanation

Porphyria cutanea tarda (PCT) is the most common porphyria, caused by UROD deficiency (acquired type 1 or hereditary type 2). Uroporphyrinogen accumulates and is oxidized to uroporphyrin, which is photoactive and causes cutaneous fragility, blisters, and hypertrichosis. Iron is a key precipitant (ferrous iron catalytically inhibits UROD). Urine is dark-red/pink and shows pink-orange fluorescence under Wood's lamp. Treatment: phlebotomy (removes iron, reduces hepatic iron burden, restoring UROD activity) is first-line; low-dose chloroquine/hydroxychloroquine mobilizes accumulated porphyrins from liver. Triggers include alcohol, estrogens, hepatitis C.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

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Written and medically reviewed by the StethoPrep medical team.