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Causes
By 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, a red, 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 exhaled.
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). 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 a genetic defect that causes 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.
It may be that an environmental factor triggers your 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
- Smoking
- Infections
- Surgery
- Stress
- Alcohol use
- Menstrual hormones
- Sun exposure
- Excess iron in your body
- Porphyria. National Digestive Diseases Information Clearinghome (NDDIC). http://digestive.niddk.nih.gov/ddiseases/pubs/porphyria/. Accessed March 24, 2009.
- Porphyria. Genetics Home Reference. Accessed March 24, 2009.
- Sassa S, et al. Understanding the porphyrias. http://www.uptodate.com/home/index.html. Accessed March 24, 2009.
- Learning about porphyria. National Human Genome Research Institute. http://www.genome.gov/pfv.cfm?pageID=19016728. Accessed March 24, 2009.
- About porphyria. American Porphyria Foundation. http://www.porphyriafoundation.com/. Accessed March 24, 2009.
- Anstey AV, et al. Liver diseases in erythropoietic protoporphyria: Insights and implications for management. Gut. 2007;56:1009.
- Sassa S, et al. Porphyria cutanea tarda, hepatoerythropoietic porphyria, and toxic porphyria. http://www.uptodate.com/home/index.html. Accessed April 2, 2009.
