Porphyria

Porphyria is an umbrella term for a group of rare conditions that involve a molecule called “heme” (or “hem”). Heme contains iron and is used in metabolic processes throughout the body. Porphyria occurs when the body cannot properly convert compounds called “porphyrins” into heme.

Although all tissues contain heme, those that use it the most are the red blood cells, liver and bone marrow. Porphyria can affect the skin, the nervous system and the gastrointestinal system. More women than men are affected.

In most cases, a combination of genetic and environmental factors triggers porphyria symptoms. There is no cure, but symptoms can often be prevented by avoiding triggers, and treatments are available to manage symptoms when they occur.

Types of porphyria#

Symptoms vary from one type of porphyria to the next. Cases are generally classified into one of three groups.

Acute porphyrias#

These mostly affect the nervous system, and the skin is occasionally affected. Acute porphyrias generally occur during adulthood and are rare before puberty or after menopause. Examples include acute intermittent porphyria and erythropoietic protoporphyria.

Symptoms may include:

• muscle pain or paralysis
• seizures
• disorientation or hallucination
• bloody (red) urine
• high blood pressure
• gastrointestinal problems such as vomiting, abdominal pain and constipation

Cutaneous porphyrias#

These affect the skin but not the nervous system. The skin becomes highly sensitive to sunlight, and exposure tends to trigger symptoms within minutes. Cutaneous porphyrias may develop during childhood. Examples include porphyria cutanea tarda and hepatoerythropoietic porphyria.

Symptoms may include:

• red, itchy, blistered, painful and swollen skin
• bloody (red) urine

Neurocutaneous porphyrias#

These affect both the skin and the nervous system, and sunlight exposure tends to rapidly trigger symptoms. Examples include variegate porphyria and hereditary coproporphyria.

What causes porphyria#

Heme is used in various metabolic processes. The body makes heme from porphyrins, which are compounds found naturally in the tissues of animals and plants. Converting porphyrins into heme requires special proteins called enzymes, and genes control the action of those enzymes.

An altered gene (or genes) can stop the body from making one or more of these enzymes. This creates a lack of heme and a build-up of porphyrins, which produces the signs and symptoms of porphyria.

Most forms of porphyria are inherited, meaning the genetic predisposition is passed from one generation to the next. The pattern of inheritance may be:

• Autosomal dominant – the altered gene is inherited from one parent and overrides the healthy gene inherited from the other parent.
• Autosomal recessive – the altered gene is inherited from both parents.

An environmental trigger is usually needed#

Not everyone who carries the altered gene will develop porphyria. An environmental trigger generally needs to be present, and triggers and responses vary between individuals. All triggers involve increased heme production. Common triggers include:

• female sex hormones that arise at puberty
• artificial hormones, such as those in some contraceptives
• certain prescription drugs, such as barbiturates, tranquillisers and sedatives
• some types of antibiotics
• sunlight
• alcohol
• cigarette smoking
• infection
• surgery
• fasting

Preventing symptoms#

Be guided by your doctor, but general suggestions for preventing symptoms include:

• In all cases, avoid known triggers; for example, do not smoke or drink alcohol.
• Protect your skin every day. When out in the sun, wear sunglasses, a brimmed hat, a long-sleeved top and long pants, and apply SPF 30+ sunscreen to exposed skin.
• Wear rubber gloves when handling chemicals or very hot water.
• Avoid perfumed soaps, and regularly apply a barrier cream to your hands.
• Eat regular meals.
• Consider wearing a medical alert bracelet or pendant, as surgery and some medications can provoke symptoms.

Diagnosis#

Because porphyria is rare, many doctors are unfamiliar with it and may not immediately recognise the symptoms. Porphyria can mimic other conditions, such as Guillain-Barré syndrome, eczema, multiple sclerosis and irritable bowel syndrome, which can delay diagnosis.

Diagnostic tests may include:

• physical examination and medical history
• urine tests to check for elevated substances, including porphyrins
• blood tests to check for high levels of porphyrins in the plasma
• a stool sample to check for excreted porphyrins
• genetic testing

Complications#

Without medical treatment, complications of porphyria may include:

• permanent hair loss
• skin scarring and permanent changes in skin pigmentation
• dehydration
• breathing problems
• high blood pressure
• low salt levels in the blood (hyponatraemia)
• kidney failure
• liver problems, which may require a liver transplant in severe cases

Treatment#

Treatment for acute porphyria may include:

• addressing the underlying cause; for example, prescribing antibiotics to treat an infection or stopping a particular medication
• pain medication
• a medication called hematin, which is a form of heme the body can use
• intravenous fluids and glucose
• admission to hospital in severe cases

Treatment for cutaneous porphyria may include oral activated charcoal, which helps to absorb excess porphyrins.

Genetic counselling#

If you have porphyria, or if it runs in your family, it may help to speak to a genetic counsellor. Genetic counsellors are health professionals qualified in both counselling and genetics.

As well as providing emotional support, they can help you understand porphyria, what causes it, how it is inherited, and what a diagnosis means for your child’s health and development and for your family. They are trained to provide information and support that is sensitive to your family circumstances, culture and beliefs.

If porphyria runs in your family, a genetic counsellor can explain the genetic testing options available to you and other relatives. You may also choose to see a genetic counsellor when planning a family, to learn your risk of passing the condition on to a child or to arrange prenatal tests. Support groups can also connect you with other individuals and families affected by porphyria.

Key points#

• In most cases, a combination of genetic and environmental factors triggers porphyria symptoms.
• There is no cure for porphyria, but avoiding triggers can prevent symptoms from developing.
• Treatments are available to manage the symptoms.
• Symptoms vary from one type of porphyria to the next.
• The three groups are acute, cutaneous and neurocutaneous porphyrias, which differ in whether they affect the nervous system, the skin, or both.

Where to get help#