CausesBy Mayo Clinic staff
Porphyria arises from a disruption in your body's production of a substance called heme.
Heme is found in all of your tissues, but the largest amounts are in your red blood cells, bone marrow and liver. Heme is a major component of hemoglobin, an iron-rich protein that gives your blood its red color. Hemoglobin enables red blood cells to carry oxygen from your lungs to all parts of your body, and to carry carbon dioxide from other parts of your body to your lungs so that it can be released when you exhale.
Eight enzymes convert chemicals called porphyrins into heme. In porphyria, an inherited mutation in one of the genes involved in heme production can cause an enzyme deficiency, which can lead to porphyrins building up in your body. Although porphyrins are normal body chemicals, it's not normal for them to build up.
Most forms are inherited
Most of the porphyrias are inherited. Some forms of the disease come from inheriting a defective gene from one of your parents (autosomal dominant pattern). Some other forms come from inheriting defective genes from both parents (autosomal recessive pattern). These gene defects cause one or more of the enzymes involved in the process of converting porphyrins to heme to be abnormal.
Just because you have inherited a gene or genes that can cause porphyria doesn't mean that you will exhibit signs and symptoms. You might have what's called latent porphyria, and never have signs and symptoms. This is the case for most carriers of the abnormal genes.
Additionally, environmental factors may trigger the development of signs and symptoms in some types of porphyria. When exposed to the trigger, your body's demand for heme production increases. This overwhelms the deficient enzyme, setting in motion a process that causes your signs and symptoms. Common triggers include:
- Drugs (barbiturates and sulfonamide antibiotics are most often cited, but others such as tranquilizers, birth control pills and sedatives also may cause symptoms)
- Dieting or fasting
- Infections or other physical stress
- Alcohol use
- Menstrual hormones
- Sun exposure
- Excess iron in your body
- Puy H, et al. Porphyrias. The Lancet. 2010;375:924.
- Learning about porphyria. National Human Genome Research Institute. http://www.genome.gov/pfv.cfm?pageID=19016728. Accessed March 22, 2011.
- Porphyria. National Digestive Diseases Information Clearinghome (NDDIC). http://digestive.niddk.nih.gov/ddiseases/pubs/porphyria/Porphyria.pdf. Accessed March 22, 2011.
- Anderson KF. Porphyrias: An overview. http://www.uptodate.com/home/index.html. Accessed March 22, 2011.
- Porphyrias. The Merck Manuals: The Merck Manual for Healthcare Professionals. http://www.merckmanuals.com/professional/print/sec12/ch155/ch155a.html. Accessed March 22, 2011.
- Desnick RJ, et al. The porphyrias. In: Fauci AS, et al. Harrison's Online. 17th ed. New York, N.Y.: The McGraw-Hill Companies; 2008. http://www.accessmedicine.com/content.aspx?aID=2883658. Accessed March 22, 2011.
- Singal AK, et al. Porphyria cutanea tarda and hepatoerythropoietic porphyria. http://www.uptodate.com/home/index.html. Accessed March 22, 2011.
- Wolanskyj AP (expert opinion). Mayo Clinic, Rochester, Minn. April 5, 2011.