The Porphyrias are a group of disorders which result from abnormalities in the biosynthesis of haem. They can be divided into two groups, the acute porphyrias and the non-acute (predominantly cutaneous) porphyrias. A number of clinically distinct disorders occur in each group. The three common acute porphyrias are:-
- Acute Intermittent Porphyria (AIP)
- Porphyria Variegata (PV)
- Hereditary Coproporphyria (HC)
AIP, PV and HC are dominantly inherited disorders. They may present in an acute phase (with neurological symptoms) or in a latent phase. PV and HC may have skin symptoms in addition to neurological symptoms.
The presenting features of an acute attack include abdominal pain and neurological symptoms ranging from peripheral neuritis to quadriplegia. If an attack is not diagnosed, the patient may be subjected to surgery, which may further aggravate the condition. In severe attacks weakness of the trunk muscles can cause repiratory failure and sometimes death.
Several factors, including exposure to a variety of common drugs, changes in hormonal status, diet or acute illness may precipitate an acute attack. During an acute attack the haem precursor, porphobilinogen (PBG) accumulates in the liver, and raised levels occur in the plasma and urine. An increase in urinary PBG therefore is strongly indicative of an acute porphyria attack
Urinary excretion of PBG is normally less than 8.8 µmol/L.
Values of 25 µmol/L and above usually indicates the presence of disease.
Urine PBG is usually greater than 100 µmol/L during an attack of porphyria.
The sample must be protected from light at all times
- A random urine sample collected without preservative or stabiliser should be used.
- Three patient identifiers from
- N.H.S. number
- Unit Number