At a Glance
Why Get Tested?
To help diagnose and sometimes to monitor porphyrias
When to Get Tested?
When a person has symptoms that suggest a neurologic porphyria (e.g., abdominal pain, tingling or numbness in the hands or feet, muscular weakness and/or alterations in thought or mood) or a cutaneous porphyria (e.g., redness, blistering, or scarring of sun-exposed skin)
Test Preparation Needed?
If a neurologic porphyria is suspected, the sample should be collected during an acute attack.
The Test Sample
What is being tested?
Porphyrins are a group of compounds defined by their chemical structure. Most porphyrin tests detect and measure the by-products of heme synthesis. Heme is an iron-containing pigment that is a necessary component of hemoglobin and a number of other proteins. The synthesis of heme is a step-by-step process that requires the sequential action of eight different enzymes. If there is a deficiency in one of these enzymes, the process is impeded and intermediate, often toxic precursor porphyrins such as uroporphyrin, coproporphyrin, and protoporphyrin build up in the body's fluids and tissues. The precursors that accumulate depend on which enzyme is deficient.
Porphyrin tests are used to help diagnose and monitor a group of disorders called porphyrias. There are several types of porphyrias, and each one is associated with a different enzyme deficiency. Most porphyrias are inherited, the result of a gene mutation. They may be classified according to the signs and symptoms of the disease as neurological, cutaneous, or both.
The porphyrias that cause neurological symptoms present with acute attacks lasting days or weeks. Signs and symptoms during the attack include abdominal pain, constipation, confusion, hallucinations, and/or seizures. There are four neurologic porphyrias: acute intermittent porphyria (AIP), variegate porphyria (VP), hereditary coproporphyria (HCP), and the very rare ALA dehydratase deficiency porphyria (ADP). Some cases of VP and HCP may also have skin-related symptoms.
The cutaneous porphyrias are associated with photosensitivity that causes redness, swelling, and a burning sensation, blistering, skin thickening, hyperpigmentation, and/or scarring. There are three cutaneous porphyrias: porphyria cutanea tarda (PCT), erythropoietic protoporphyria (EPP), and congenital erythropoietic porphyria (CEP). For more information about each disease, see the article on Porphyria.
To diagnose porphyrias, clinical laboratories measure porphyrins and their precursors in urine, blood, and/or stool. Testing may include measurement of one or more of the following:
- Porphobilinogen (PBG), a porphyrin precursor, in urine
- Delta-aminolevulinic acid (ALA), another porphyrin precursor, in urine
- Porphyrins (uroporphyrin, coproporphyrin, and protoporphyrin) in urine, blood, or stool
Specialized laboratories may offer testing for one or more of the affected enzymes. The most commonly measured enzyme is porphobilinogen deaminase (PBG-D) in red blood cells, which tests for acute intermittent porphyria. A few laboratories offer genetic testing for specific gene mutations that cause one of the porphyrias, but this type of testing is not widely available.
How is the sample collected for testing?
The sample type depends on the porphyrin tests ordered by the doctor. It may include one or more of the following:
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
If a neurologic porphyria is suspected, the sample should be collected during an acute attack.
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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.
Sources Used in Current Review
Frank, E. and Leiferman, K. (Updated 2011 June). Porphyrias. ARUP Consult [On-line information]. Available online at http://www.arupconsult.com/Topics/Porphyrias.html?client_ID=LTD through http://www.arupconsult.com. Accessed October 2011.
Mir, M. and Logue, G. (Updated 2009 October 1). Porphyria Overview. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/1389981-overview through http://emedicine.medscape.com. Accessed October 2011.
Dugdale, D. (2011 February 28). Porphyrins – blood. Medline Plus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003372.htm. Accessed October 2011.
Dugdale, D. (2011 February 28). Porphyrins – urine. Medline Plus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003614.htm. Accessed October 2011.
Thunell, S. (Updated 2008 August). Overview of Porphyrias, Acute Porphyrias, Cutaneous Porphyrias. Merck Manual for Healthcare Professionals [On-line information]. Available online through http://www.merckmanuals.com. Accessed October 2011.
(© 1995–2011). Unit Code 81052: Porphyrins Profile. Mayo Clinic Mayo Medical Laboratories [On-line information]. Available online at http://www.mayomedicallaboratories.com/test-catalog/Overview/81052 through http://www.mayomedicallaboratories.com. Accessed October 2011.
(Reviewed 2009 July). Porphyria. Genetics Home Reference [On-line information]. Available online at http://ghr.nlm.nih.gov/condition/porphyria through http://ghr.nlm.nih.gov. Accessed October 2011.
Pagana, K. D. & Pagana, T. J. (© 2011). Mosby's Diagnostic and Laboratory Test Reference 10th Edition: Mosby, Inc., Saint Louis, MO. Pp 767-768.
Harmening D. Clinical Hematology and Fundamentals of Hemostasis, Fifth Edition, F.A. Davis Company, Philadelphia, 2009, Pp 130-131.
Kasper DL, Braunwald E, Fauci AS, Hauser SL, Longo DL, Jameson JL eds (2005). Harrison's Principles of Internal Medicine, 16th Edition, McGraw Hill, Pp 2303-2308.
Schreiber WE. Iron and porphyrin metabolism. In: Clinical Chemistry: Theory, Analysis and Correlation, 5th Ed (LA Kaplan, AJ Pesce, Eds), Mosby, St. Louis, 2009, Pp. 755-770.
Sources Used in Previous Reviews
Schreiber WE. Iron, porphyrin and bilirubin metabolism. In: Clinical Chemistry: Theory, Analysis and Correlation, 4th Ed (LA Kaplan, AJ Pesce, SC Kazmierczak, Eds), CV Mosby, St. Louis, 2003, pp. 657-674.
Pagana, Kathleen D. & Pagana, Timothy J. (2001). Mosby's Diagnostic and Laboratory Test Reference 5th Edition: Mosby, Inc., Saint Louis, MO. Pp325, 670-672.
(2003 March) Porphyria. NIH Publication No. 03-4632, National Digestive Diseases Information Clearinghouse (NDDIC). Available online at http://digestive.niddk.nih.gov/ddiseases/pubs/porphyria/index.htm through http://digestive.niddk.nih.gov.
(© 2004) Porphyria Overview. American Porphyria Foundation. Available online at http://www.porphyriafoundation.com/about_por/overview/index.html through http://www.porphyriafoundation.com.
(© 2004) Testing. American Porphyria Foundation. Available online at http://www.porphyriafoundation.com/about_por/testing/index.html through http://www.porphyriafoundation.com.
(© 2004). Three articles [see below]. American Porphyria Foundation, For Physicians. Available online through http://www.porphyriafoundation.com:
AIP, HCP, VP, & ADP, Diagnosis.
Cohen, E. (2003 June 5, Update). Porphyria. MedlinePlus Medical Encyclopedia. Available online: http://www.nlm.nih.gov/medlineplus/ency/article/001208.htm.
(© 1995-2004) Porphyrias, Introduction. The Merck Manual 2nd Home Edition, Section 12. Disorders of Nutrition and Metabolism, Chapter 160. Available online at http://www.merck.com/mrkshared/mmanual_home2/sec12/ch160/ch160a.jsp through http://www.merck.com.
(© 1995-2004). Chapter 14. The Porphyrias. The Merck Manual of Diagnosis and Therapy, Section 2. Endocrine And Metabolic Disorders. Available online at http://www.merck.com/mrkshared/mmanual/section2/chapter14/14a.jsp through http://www.merck.com.
(© 2004). Six articles [see below]. ARUP's Guide to Clinical Laboratory Testing. Available online through http://www.aruplab.com
Aminolevulinic Acid (ALA), Urine.
Porphobilinogen (PBG) Deaminase, Erythrocyte.
Porphobilinogen (PBG), Urine.
Porphyrins, Blood and Serum.
Pagana, Kathleen D. & Pagana, Timothy J. (© 2007). Mosby's Diagnostic and Laboratory Test Reference 8th Edition: Mosby, Inc., Saint Louis, MO. Pp 744-745.
Clarke, W. and Dufour, D. R., Editors (2006). Contemporary Practice in Clinical Chemistry, AACC Press, Washington, DC. Pp 439, 440t.
Wu, A. (2006). Tietz Clinical Guide to Laboratory Tests, Fourth Edition. Saunders Elsevier, St. Louis, Missouri. Pp 874-879.
Levin, M. (2007 March 8, Updated). Porphyrins urine. MedlinePlus Medical Encyclopedia. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003614.htm. Accessed on 4/21/08.
Alexander, D. (2007 May 29, Updated). Porphyrins - Blood. MedlinePlus Medical Encyclopedia. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003372.htm. Accessed on 4/21/08.
Frye, R. and DeLoughery, T. (2007 June 26). Pophyria, Acute. emedicine. Available online at http://www.emedicine.com/ped/TOPIC1870.HTM. Accessed on 4/21/08.
(© 2007). About Porphyria and Why laboratory tests are important for diagnosis of porphyrias. American Porphyria Foundation. Available online at http://www.porphyriafoundation.com/about_por/index.html through http://www.porphyriafoundation.com. Accessed on 4/20/08.