Porphyria cutanea tarda is a blistering cutaneous photosensitivity. It is the most common porphyria. It is caused by a defect in uroporphyrinogen decarboxylase or hepatic damage.
- Precipitating factors
- Alcohol
- Hepatitis C
- Oestrogen-containing medications
- Iron-containing supplements
- Associated conditions
- Alcoholism
- Liver disease
- Haemochromatosis
- Chronic hepatitis C
- Oral contraceptives
- HFE gene mutaitons
- Signs and symptoms
- Fragile skin that blisters easily
- Vesicles and bullae on sun-exposed sites
- Milia
- Hyperpigmentation over affected sites
- Hypertrichosis over the cheeks and temples
- Sclerodermoid changes in chronic cases
- Calcified plaques (pseudoporphyria) in chronic cases
- Systemic symptoms are uncommon
- Pain is not a major concern
- Investigations
- Urine porphyrin analysis
- Reddish-brown discolouration of urine (port-wine urine) that may fluoresce pink under Wood’s lamp
- Elevated uroporphyrin and heptacarboxylporphyrin
- Faecal porphyrin analysis to differentiate porphyria cutanea tarda from other forms
- Iron studies
- Iron overload
- Liver function tests to assess for hepatic involvement or co-existing liver disease
- Viral hepatitis serology
- Urine porphyrin analysis
- Treatment
- Avoid exposure to alcohol, estrogen, primidone, and other hepatotoxins
- Sun protection
- Wound care for blisters and erosions
- Phelbotomy (first-line treatment) to remove iron
- Remove 450 – 500 ml of blood every 2 weeks until ferritin normalizes
- Low-dose hydroxychloroquine – an alternative first-line treatment – increases porphyrin excretion
- Monitor liver function and serum ferritin during treatment
- Long-term follow-up since relapse can occur
- Prognosis
- Complete resolution in 2 months to 2 years after stopping triggers
