Inherited disorders: Porphyria
These pages about porphyria were prepared in partnership with BIPNET, the British and Irish Porphyria Network, and the UK Porphyria Medicines Information Service, Cardiff. We'd like to thank these partners for contributing their clinical expertise and support.Porphyrias are a group of inherited metabolic disorders of the haem biosynthesis pathway, caused by a fault with one of the enzymes involved. Haem is a molecule created by human metabolism and is used to build larger molecules such as haemoglobin, myoglobin, and cytochrome. Porphyrias lead to accumulation of neurotoxic and/or phototoxic haem precursors, and so these conditions are characterised by acute neurological and visceral symptoms ('neurovisceral crises') and/or skin lesions.
What type of porphyria?
It is important to understand the type of porphyria your patient has been diagnosed with, and in particular whether it is acute porphyria or non-acute porphyria.
In practice, acute intermittent porphyria (AIP), variegate porphyria (VP) and hereditary coproporphyria (HCP) are the conditions that pharmacists may see presenting acutely. Many factors can precipitate an acute attack by increasing the body's need for haem, and they act cumulatively as shown in the diagram below. In patients with porphyria the haem is produced, but precursors in the pathway may accumulate and cause symptoms. In addition, several patient factors can predispose individuals to developing an attack.
Four types of acute porphyrias affect the nervous system (AIP, VP, HCP, ADP). Two of these can also affect the skin (VP,HCP). Symptoms for acute porphyrias develop over hours or days and last for days or weeks.
Early symptoms of an acute attack can include: tachycardia, acute severe abdominal pain, nausea and vomiting, constipation, peripheral motor neuropathy, and paraesthesia. This may progress to severe cardiovascular, neurological and psychiatric symptoms, and a progressive, irreversible neuropathy. Ultimately, this can be fatal if untreated.
Three types of cutaneous porphyrias affect only the skin and cause chronic, or long lasting, symptoms (PCT, EPP, CEP). People with cutaneous porphyria may develop skin symptoms—such as blistering or pain—after their skin is exposed to sunlight.