The porphyrias are inherited or acquired disorders of certain enzymes in the haem biosynthetic pathway that is responsible for the synthesis of haemoglobin, myoglobin and cytochrome. They are broadly classified as hepatic porphyrias or erythropoietic porphyrias based on the site of their overproduction and subsequent accumulation (or their chemical precursors).
Hepatic porphyria: abdominal pain, vomiting, acute neuropathy, seizures and mental disturbances; cardiac arrhythmias and tachycardia may develop as the autonomic nervous system is affected Erythropoietic porphyria: photodermatitis, blisters, necrosis of the skin and gums, itching and increased hair growth
|Sample & container required||EDTA (lavender top) or heparin (green top) protected from light, preferably collect during an attack|
|Sample volume||5 mL whole blood|
|Transport storage||Blood must be protected from light at all times|
|Turnaround time||Up to 6 weeks|
Not currently performed in house; this is a referred test. Haemolysed samples are unsuitable for analysis. Separation of cells from plasma makes this less likely if there is a delay in sending the sample to the referral centre.