What is porphyria cutanea tarda?
Porphyria cutanea tarda (PCT) is a rare condition which is characterised by blistering and fragility of the skin in sun exposed areas. The breaks in the skin and blisters often heal with scarring and small superficial cysts called milia may form.
PCT is the most common type of porphyria. It occurs worldwide.
Variegate porphyria has skin changes similar to PCT plus acute neurologic problems. It is mainly seen in South Africa where it is reasonably common and also in Chile.
There are other forms of porphyria that may result in cutaneous manifestations and attacks of neurologic symptoms that we are not covering here.
What causes it?
Heme is the iron-containing compound found in red blood cells used to carry oxygen which is broken down in a series of steps and ultimately excreted in the urine.
PCT results from reduced activity of the enzyme uroporphyrinogen decarboxylase in the liver which is involved in the breakdown of heme. If the heme is not broken down in the usual way, porphyrins accumulate in the skin. These compounds absorb UV energy that is released in the skin, creating changes that lead to blistering, fragility and scarring of the skin.
There are two types of PCT.
- Type 1 is not inherited and represents about 80% of cases of PCT. Type 1 PCT develops as a result of reduced levels of the enzyme in the liver due to:
- Excessive deposition of iron
- Viral infections such as hepatitis C and HIV
- Alcohol and oestrogen use
- Environmental factors such as exposure to hexachlorobenzene, dioxins and other halogenated hydrocarbons
- Fatty liver and diabetes which cause liver damage are associated with PCT.
- Type 2 is inherited and is extremely rare. It affects every generation of a family (autosomal dominant). In type 2, the enzyme is deficient in both red blood cells and the liver.
What does it look like?
Individuals with PCT suffer from photosensitivity which means the skin is damaged by sunlight. The skin changes appear on sun exposed areas of the body including the backs of hands, forearms, ears and the face.
PCT presents as fragile skin with blisters, erosions (shallow ulcers), crusts, milia and scars. Darkening of the skin (post-inflammatory hyperpigmentation), abnormal growth of hairs particularly on the sides of the face (hypertrichosis), scarring and hardening of the skin (sclerodermoid changes) may also be present in the sun exposed areas.
The condition most commonly affects individuals in midlife between 30 to 50 years. However, it can also affect children in rare cases.
How is it diagnosed?
Usually the doctor will suspect PCT as a result of taking a medical history and examining the skin.
A number of medications may cause photosensitivity eruptions that may resemble the changes seen in PCT. These include non-steroideal anti-inflammatory agents (NSAIDs, e.g. naproxen and mefanamic acid), antibiotics (e.g. nalidixic acid, tetracycline, doxycycline and ciprofloxacin) and diuretics (e.g. frusemide, hydrochlorthiazide).
The diagnosis will be confirmed by undertaking some specific investigations.
- Urine and blood tests are needed to measure porphyrin levels. A urine sample from a person with PCT turns red brown after several hours’ exposure to light.
- A skin biopsy will be needed to confirm the diagnosis and to exclude other blistering diseases.
- Blood tests to check the levels of iron, haemoglobin, liver enzymes, glucose, and evidence of viral hepatitis or HIV will be needed.
- If a hereditary form of PCT is suspected, the doctor may suggest genetic counselling.
How is it treated?
All individuals with PCT should be assessed and treated for associated medical problems.
It is essential that individuals avoid UV light exposure by wearing protective clothing and applying broad-spectrum sunscreens regularly to prevent further damage to the skin.
Individuals should eliminate aggravating factors such as alcohol ingestion, oestrogen therapy and drugs causing photosensitivity if applicable.
In those with an iron overload, regular phlebotomy, which involves taking blood out of the body, or iron chelation, which involves administrating medication to remove extra iron from the body, may be indicated.
Low dose antimalarial medication may help with excretion of the porphyrins.
What is the likely outcome of porphyria cutanea tarda?
When affected individuals avoid triggering factors and comply with specific treatments suggested by the doctor, the skin lesions will most likely disappear over time.
All individuals with PCT require regular follow up to monitor their response to treatment and to ensure that no serious adverse events to the treatment develop.
This information has been written by Dr Shelley Ji Eun Hwang and A/Professor Pablo Fernandez-Penas
Updated 1 December 2015