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Porphyria (cont.)

What are the types of porphyria?

The table below lists each type of porphyria and the deficient enzyme responsible for the disorder. Porphyrias are often classified as acute or cutaneous. Acute types of porphyria affect the nervous system, whereas cutaneous types mainly affect the skin. Two forms of porphyria - hereditary coproporphyria and variegate porphyria -- may be either acute or cutaneous, or both.

Types of Porphyria
Type of Porphyria Deficient Enzyme
Acute Porphyrias
ALAD porphyria delta-aminolevulinic acid dehydratase
acute intermittent porphyria porphobilinogen deaminase
hereditary coproporphyria coproporphyrinogen oxidase
variegate porphyria protoporphyrinogen oxidase
Cutaneous Porphyrias
congenital erythropoietic porphyria uroporphyrinogen III cosynthase
porphyria cutanea tarda uroporphyrinogen decarboxylase (~50% deficiency)
hepatoerythropoietic porphyria uroporphyrinogen decarboxylase (~90% deficiency)
hereditary coproporphyria coproporphyrinogen oxidase
variegate porphyria protoporphyrinogen oxidase
erythropoietic protoporphyria ferrochelatase

The most common type of porphyria overall is porphyria cutanea tarda. In the United States, acute intermittent porphyria is the most common acute porphyria.

What causes porphyria?

Most porphyrias are inherited disorders, meaning they are caused by abnormalities in genes passed from parents to children. Scientists have identified the genes for all eight enzymes in the heme pathway. Some forms of porphyria result from inheriting an abnormal gene from one parent. Other forms are due to inheriting two abnormal genes - one from each parent. The risk that members of an affected family will have the disease or transmit it to their children depends on the type of porphyria.

One type of porphyria -- porphyria cutanea tarda -- is most often an acquired disorder. It occurs when factors other than genes cause an enzyme deficiency in the liver.

Porphyria can be triggered by:

  • Drugs such as barbiturates, tranquilizers, birth control pills, and sedatives
  • Chemicals
  • Fasting
  • Smoking
  • Drinking alcohol, especially heavy drinking
  • Infections
  • Excess iron in the body
  • Emotional and physical stress
  • Menstrual hormones
  • Exposure to the sun
Medically Reviewed by a Doctor on 4/3/2014

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Source: MedicineNet.com
http://www.medicinenet.com/porphyria/article.htm

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