Conditions · Metabolism: heme, bilirubin and iron
Porphyria cutanea tarda !
The most common porphyria: blisters and fragile skin on the backs of the hands and the face, due to failure of a liver enzyme.
Updated 2026-11-01
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In biochemistry
What it is
Chronic cutaneous porphyria caused by low uroporphyrinogen decarboxylase activity in the liver, which builds up photosensitising porphyrins in the skin.
Who gets it
It is the most common porphyria worldwide; it appears in adults, more often in men. In Latin America it is linked mainly to alcohol, hepatitis C and HIV.
Causes
- Type 1 (acquired, the majority): UROD inhibition in the liver
- Type 2 (familial): one mutated UROD allele plus triggers
Risk factors
- Alcohol
- Hepatitis C and HIV
- Iron overload, HFE mutations
- Estrogens and smoking
Pathophysiology
Iron and oxidative stress in the hepatocyte turn some uroporphyrinogen into uroporphomethene, which inhibits UROD. Uroporphyrin and highly carboxylated porphyrins build up; they reach the skin, absorb visible light and produce radicals that split the epidermis from the dermis.
Symptoms and signs
- Blisters and erosions on the backs of the hands, forearms and face after sun exposure
- Fragile skin that tears with minor trauma
- Scars, milia and dark patches
- Excess hair on the cheeks and temples (hypertrichosis)
- Reddish or tea-coloured urine
Diagnosis
- Clinical
- Blisters and fragility on sun-exposed skin in an adult with alcohol use, hepatitis C or high iron; there are no abdominal attacks.
- Tests
- Markedly raised urine porphyrins dominated by uroporphyrin and heptacarboxylporphyrin; normal porphobilinogen; plasma porphyrins with a typical fluorescence peak; ferritin and transferrin saturation; hepatitis C, HIV and HFE testing.
- Imaging
- Liver ultrasound to look for steatosis, cirrhosis or hepatocellular carcinoma.
Treatment
- Procedure
- Regular phlebotomy to lower liver iron to a low-normal ferritin
- Medical
- Low-dose hydroxychloroquine regimen when phlebotomy is not possible
- Medical
- Antiviral treatment of hepatitis C, which often leads to remission
- Lifestyle
- Stopping alcohol, smoking and estrogens; protecting the skin from visible light and sun
Complications
- Scarring and alopecia
- Cirrhosis
- Hepatocellular carcinoma
Prognosis
With treatment lesions resolve within months; it can relapse if triggers return.
Test yourself
Think of the answer, then tap the question to see it.
Which enzyme fails in porphyria cutanea tarda?
Liver uroporphyrinogen decarboxylase.
Why does phlebotomy improve porphyria cutanea tarda?
It lowers liver iron, which drives formation of the UROD inhibitor.
Which viral infection is often associated with porphyria cutanea tarda?
Hepatitis C (HIV as well).
Related conditions
- Hereditary hemochromatosis
- Acute intermittent porphyria
- Cirrhosis
- Hepatocellular carcinoma
- Viral hepatitis
- HIV infection and AIDS
Educational information, not medical advice. For any symptom, see a health professional.
Sources: Porphyria: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2026); UROD gene: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2026); Porphyrins urine test: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011).
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