What is Porphyria?
Porphyria is the name given a group of very rare metabolic disorders that occur when your body is unable to produce enough of a substance called haem.
Haem is required for many bodily functions. It is a component of haemoglobin, a vital protein which helps transport oxygen around your body and the pigment that gives red blood cells their colour. Haem also helps to form many other important proteins and is found in all body tissues, but mostly in red blood cells, bone marrow and the liver.
To produce haem, your body needs to convert two simple substances, aminolaevulinate acid (ALA) and porphobilinogen (PBG), known as porphyrin precursors, into more complicated substances called porphyrins. These are then converted from one type of porphyrin into another to form, haem.
The steps in this process, or ‘pathway’, are carried out by seven specialised proteins known as enzymes.
If you inherit or develop a defect (usually termed a ‘deficiency’) in these enzymes, the process may not work properly and can cause porphyrins to build up in your body.
This accumulation can either affect the nervous system to provoke ‘acute attacks’ of physical pain or cause damage to your skin – sometimes both.
It can also cause a person’s urine to turn a reddish-purple colour. In fact, the terms ‘porphyrin’ and ‘porphyria’ stem from the Greek word for purple, ‘porphyrus’.
The symptoms you have will depend on which enzyme is affected. There are more than seven types of porphyria, each categorised according to the particular enzyme deficiency and the symptoms associated with it.
Because of this it is diffi cult to talk about porphyria in general terms. It is possible to divide the disorders into those that mostly affect the brain, known as acute porphyrias, and those that cause skin problems, called cutaneous porphyrias.
‘Cutaneous’ means relating to the skin; disorders that share the characteristics of both are called neurocutaneous porphyrias.
Acute porphyrias are acute intermittent porphyria (AIP), the most common form in the UK and the most severe, and aminolevulinate dehydratase defi ciency porphyria (ADP). This form is similar to AIP but extremely rare.
Cutaneous porphyrias are porphyria cutanea tarda (PCT), the most common of the skin disorders and the most common globally; erythropoietic porphyria (EPP), a very uncommon form that causes symptoms very early in life; and the rarest form, congenital erythropoietic porphyria (CEP), which also occurs early.
Porphyrias causing both acute and cutaneous disorders are hereditary coproporphyria (HCP) and variegate porphyria (VP).
Porphyria can appear in childhood, as seen in erythropoietic porphyria (EPP), but the onset is usually between the ages of 20 and 40 and affects women more than men.
Acute forms can cause serious damage to your liver and kidneys. In some severe cases, people may need a liver transplant. Attacks or seizures can lead to complications such as respiratory failure which can be fatal if not treated. Around 1% of acute attacks of porphyria are fatal.
It is important that the type of porphyria you have is diagnosed as soon as possible. With good management, severe symptoms can be avoided and most people with porphyria (‘porphyriacs’) do in fact lead relatively normal lives.