Related Subjects:
|Acute Porphyrias
|Variegate Porphyria
|Acute Intermittent Porphyria (AIP)
|Porphyria Cutanea Tarda (PCT)
|Porphyria Testing
Porphyria Cutanea Tarda (PCT) causes blistering of the backs of the hands ✋ and forehead, which usually heals with small scars and milia (tiny keratin cysts).
Inherited form: autosomal dominant mutation in the UROD gene.
📖 About
- PCT is the most common type of porphyria.
- Porphyrins are photoactive molecules that strongly absorb light in the violet spectrum.
- Photoexcited porphyrins generate reactive oxygen species → oxidative damage to skin structures → cutaneous photosensitivity.
🧬 Aetiology
- Deficient activity of the heme-synthetic enzyme uroporphyrinogen decarboxylase (UROD), mainly in the liver.
- ~80% acquired; ~20% familial (AD inheritance of UROD mutations).
- Porphyrins accumulate in the liver, plasma, and skin.
- Precipitants: alcohol 🍷, oestrogens, hepatitis C, HIV, smoking 🚬, and iron overload (e.g. haemochromatosis gene mutations).
🩺 Clinical Features
- 📸 Photosensitivity: blistering on sun-exposed skin (hands, forearms, face).
- 💨 Skin fragility: erosions and bullae even after minor trauma.
- 🌿 Hypertrichosis: excess facial hair (especially on cheeks/temples).
- ✨ Milia: small keratin cysts after healing.
- Scarring, dyspigmentation, and chronic disfigurement may develop.
🔍 Investigations
- 🧪 Urine porphyrins: markedly elevated (dark red urine, pink fluorescence under Wood’s lamp).
- 💩 Faecal coproporphyrins: often raised.
- RBC UROD enzyme assay (confirms inherited deficiency if available).
- Check iron studies (serum ferritin, transferrin saturation).
- Screen for associated conditions: hepatitis C, HIV, haemochromatosis gene mutations.
💊 Management
- ⚡ General measures: strict photoprotection, avoid alcohol, oestrogens, smoking, and hepatotoxic drugs.
- 🩸 Therapeutic phlebotomy: mainstay treatment. Regular venesection reduces iron stores, relieving ferro-inhibition of UROD.
- Target: serum ferritin at lower reference limit.
- Ensure Hb > 11 g/dL before phlebotomy.
- 💊 Low-dose chloroquine/hydroxychloroquine: mobilises porphyrins from liver (use cautiously to avoid hepatotoxicity).
- 🧷 Iron chelation (desferrioxamine) if phlebotomy not feasible.
- 📌 Treat underlying triggers: antiviral therapy for hepatitis C, iron overload correction.
Sample Handling: All specimens must be protected from light.
- 🩸 Blood – Purple EDTA.
- 💧 Urine – White plain 20 mL universal container.
- 💩 Faeces – Blue 20 mL faecal universal container.
🧾 Clinical Case – Porphyria Cutanea Tarda
A 52-year-old man with chronic alcohol use and hepatitis C presents with
fragile, blistering skin on the backs of his hands after sun exposure,
along with facial hypertrichosis and dark urine.
Labs show elevated plasma porphyrins and mild LFT derangement, consistent with
Porphyria Cutanea Tarda. Management included venesection, sun avoidance, and stopping alcohol.
📚 References
- DermNet NZ – Porphyria Cutanea Tarda.
- Rook’s Textbook of Dermatology.
- British Journal of Dermatology – PCT Guidelines.
