All porphyria diagnoses are confirmed by biochemical testing. “Clinical diagnoses” without positive biochemical results are not considered diagnostic of porphyria.
Biochemical testing, or blood and urine tests, are the first ones that should be done when a type of porphyria is suspected. The specific biochemical tests depend on the symptoms. For all the first line tests the results will be very high if someone has porphyria. Small increases in these tests are generally not diagnostic.
Each type of porphyria (with exception of Sporadic PCT) is caused by a mutation, or change, in the genetic material that codes for a specific enzyme in the heme pathway. This testing is done on a blood, saliva, or mouth swab sample, generally after the biochemical testing has been done in someone who was recently diagnosed, or in family members of someone with a porphyria.
The different genes that cause the porphyrias are:
|Type of Porphyria||Gene|
|ALA-Dehydratase Porphyria (ADP)||ALAD|
|Acute Intermittent Porphyria (AIP)||HMBS|
|Congenital Erythropoietic Porphyria (CEP)||UROS|
|Porphyria Cutanea Tarda (PCT), familial form||UROD|
|Hepatoerythropoietic Porphyria (HEP)||UROD|
|Hereditary Coproporphyria (HCP)||CPOX|
|Variegate Porphyria (VP)||PPOX|
|Erythropoietic Protoporphyria (EPP)
X-linked Protoporphyria (XLP)
A very small number of people who have a biochemical diagnosis of porphyria may not have a gene change found.
Recommendations for testing family members depends on how the different porphyrias are inherited.
For more information on who should be tested in your family talk to a porphyria specialist or genetic counselor