Conditions and symptoms
What Is Porphyria Cutanea Tarda (PCT)? Plain Guide
Porphyria cutanea tarda · say it: por-FEER-ee-uh kyoo-TAY-nee-uh TAR-duhAlso written: PCT, porphyria, cutaneous porphyria
Short answer
Porphyria cutanea tarda (PCT) is a condition where a liver enzyme works poorly, causing fragile, blistering skin on sun-exposed areas.
What it means
Porphyria cutanea tarda, or PCT, is the most common type of porphyria, a group of conditions where the body has trouble making heme, part of the red pigment in blood. In PCT, an enzyme in the liver works poorly and substances called porphyrins build up. They make the skin very sensitive to light, so blisters, fragile skin, scarring and extra hair growth appear on sun-exposed areas such as the backs of the hands and face. Urine may look darker than usual.
PCT appears on medicine labels in two ways. Some medicines, such as hydroxychloroquine and chloroquine, carry a caution in people with porphyria, because they may make it worse at higher doses; under specialist care, low doses are sometimes used to treat PCT. Other labels, such as those for estrogens, list porphyria as a condition that may be triggered or worsened. Alcohol, iron overload, hepatitis C and smoking are also known triggers.
PCT is different from acute porphyrias, which cause sudden attacks of stomach pain and nerve symptoms. It is also different from simple sunburn or a photosensitivity reaction to a medicine.
Where you may see it
- Cautions in the 'Warnings' section of antimalarial and estrogen labels
- Dermatology and liver clinic letters
- Urine and blood porphyrin test reports
📄 How it looks on a report
Use with caution in patients with porphyria. Exacerbation of porphyria may occur.
🙅 What it does not mean
- PCT is not an allergy to the sun; it is caused by a build-up of porphyrins.
- Having PCT does not mean every medicine is unsafe, but each should be checked.
- Blistering skin is not always PCT; other conditions can look similar.
🗒️ Questions to ask your doctor
💊 Medicines whose labels mention “Porphyria cutanea tarda”
Plain-English explanations of each medicine, from its official FDA label.
- Hydroxychloroquine
an antimalarial and antirheumatic drug, which means it is used for malaria and for certain joint and immune conditions
- Phenytoin
An anti-epileptic (seizure) medicine. The label describes it as related to barbiturates in chemical structure, and it belongs to the hydantoin group of medicines.
- Rifampin
an antibiotic of the rifamycin type
🔗 Read more from trusted sources
- “Porphyria cutanea tarda” on MedlinePlus ↗
US National Library of Medicine
- NCI Dictionary definition ↗
US National Cancer Institute: “porphyria cutanea tarda”
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