Porphyria

What is porphyria?

Chemicals in the body called porphyrins are key to producing haem - a molecule that's vital in red blood cells for carrying oxygen. Two substances known as porphyrin precursors are converted into haem, via a series of steps, each step controlled by a particular protein enzyme.

In porphyria there is a deficiency of these enzymes, so the process is blocked and porphyrins (and their precursors) accumulate to toxic levels in the body.

Drug treatments are one of the major causes of acquired porphyria and are also a major trigger of acute attacks in inherited porphyria.

Symptoms

There are at least seven types of porphyria. Each is caused by a slightly different enzyme deficiency with a different pattern of symptoms.

The different types are usually classified as acute or non-acute.

People with an acute type porphyria experience episodes of severe pain and disruption of the nervous system that may develop rapidly, over several hours, causing a wide range of symptoms throughout the body.

An acute attack is triggered when levels of porphyrins and porphyrin precursors escalate. This may be due to drugs that interfere with porphyrin metabolism in the body, alcohol, smoking, infection and reduced calorie intake. Pregnancy may also trigger an attack as hormone levels change, while some women have regular attacks prior to their periods.

Symptoms include:

• Abdominal pain.
• Stomach cramps.
• Nausea.
• Vomiting and constipation.
• Pain elsewhere in the body, especially in the back and limbs.
• Muscle weakness.

In extreme cases there may be:

• Heart palpitations and a rapid heartbeat.
• High blood pressure.
• Anxiety.
• Confusion.
• Seizures.
• Paralysis.

An acute attack of porphyria can be fatal, although this is very rare. Severe attacks need to be treated in hospital but mild attacks may go unnoticed or be misdiagnosed.

In non-acute porphyria, the primary problem is with the skin. Some types of the condition develop during a lifetime, probably as a result of factors including high alcohol consumption, abnormal levels of iron or oestrogens and hepatitis infections that combine to cause an enzyme deficiency in the liver.

Other types are inherited, causing skin problems initially, although the liver may be affected in later life. Skin exposed to light (such as hands, feet and face) becomes fragile and develops blisters and sores. The skin may be easily damaged, and even the slightest knock causes it to break open, while healing is slow.

These changes tend to develop during adult life. Chronic damage leads to thin, darkened and scarred skin that may become unusually hairy.

In some types, the skin problems start in early childhood and tend to be more severe. Reaction to the sun is swift, with burning and stinging occurring soon after exposure.

Treatment and recovery

There's no cure for porphyria but careful control of trigger factors means most people lead a normal life.

A large number of medicines, including many common antibiotics and sleeping pills, may precipitate an acute attack. In general, those affected should:

• Only take medication when absolutely necessary.
• Never take a new medicine unless it's been checked as suitable for people with porphyria.
• Be careful with over-the-counter treatments, such as vitamins or herbal therapies.
• Inform doctors they have porphyria before being given an anaesthetic.

Avoiding the sun and protecting the skin from injury is essential for those whose skin is affected. Meticulous skin care can reduce long-term damage.

For those affected by certain types of porphyria, it's vital to avoid triggers such as alcohol or certain medicines (such as the contraceptive pill).

Treatment using venesection (removal of a unit of blood at regular intervals) may also help in some cases.

All the genetic problems causing porphyria have now been identified, and genetic testing for carriers can now be done.

Advice and support

British Porphyria Association

• Tel: 01474 369 231
• Email: helpline@porphyria.org.uk
• Website: www.porphyria.org.uk