Most of the porphyrias are inherited conditions. The genes for all the enzymes in the heme pathway have been identified. Some forms of porphyria result from inheriting one altered gene from one parent (autosomal dominant). Other forms result from inheriting two altered genes, one from each parent (autosomal recessive). Each type of porphyria carries a different risk that individuals in an affected family will have the disease or transmit it to their children.
Porphyria cutanea tarda (PCT) is a type of porphyria that is most often not inherited. Eighty percent of individuals with PCT have an acquired disease that becomes active when factors such as iron, alcohol, hepatitis C virus (HCV), HIV, estrogens (such as those used in oral contraceptives and prostate cancer treatment), and possibly smoking, combine to cause an enzyme deficiency in the liver. Hemochromatosis, an iron overload disorder, can also predispose individuals to PCT. Twenty percent of individuals with PCT have an inherited form of the disease. Many individuals with the inherited form of PCT never develop symptoms.
If you or someone you know has porphyria, we recommend that you contact a genetics clinic to discuss this information with a genetics professional. To find a genetics clinic near you, contact your primary doctor for a referral.
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