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Porphyrias are a group of extremely rare disorders which affect the skin or nervous system, resulting in severe abdominal discomfort. Porphyria disorders are generally inherited, which means they are the result of genetic abnormalities passed from a parent to a child. When someone has porphyria, cells do not convert body chemicals known as polyphorins into heme, which is what gives blood its red color.
What Is Heme?
The human body manufactures heme in the liver and red blood cells.
If the body has difficulties making heme, it is the result of any of these eight enzymes being at a low level or deficient. Porphyrins and porphyrin precursors of heme will buildup in the human body and as a result, a person can become very ill.
How Are Different Porphyrias Classified?
Porphyrias are classified in different systems. The most accurate classification for a specific type of porphyria is due to the specific enzyme deficiency. Another way to classify porphyrias is to look at the symptoms each one causes, neurological symptoms are caused by acute porphyrias, while those that cause photosensitivity are of the cutaneous variety. Lastly, the third way to classify a specific type of porphyria is using a system based on whether the excess precursors originate from the liver or in the bone marrow. Some types of porphyrias are classified as being one or more of these specific categories.
Porphyria: How Common Is It?
According to US National Library of Medicine, the exact number of porphyria cases is unknown. However, estimates put it at 1 in 500 or possibly as high as 1 in 50,000 people worldwide. Overall, cutaneous porphyria is the most common type of all cases diagnosed. For some types of porphyria, the exact prevalence is not known because many individuals with a genetic mutation associated with the disease with remain asymptomatic throughout their life.
Different Genes Related to Porphyria
- ALAD: Aminolevulinate dehydratase, responsible for instructing manufacture of the delta-aminolevulinate dehydratase.
- ALAS2: Aminolevulinate, delta-, synthase 2. The ALAS2 gene is responsible for instructing the manufacture of the 5-aminolevulinate synthase 2 or erythroid ALA-synthase.
- CPOX: Coproporphyrinogen oxidase, provides instructions for the manufacture of the coproporphyrinogen oxidase enzyme.
- FECH: Ferrochelatase, the gene provides instructions on making the ferrochelatase enzyme.
- HFE: Hemochromatosis, the gene provides instructions for producing a protein located on the surface of cells located in the liver and intestines.
- HMBS: Hydroxymethylbilane synthase, the gene provides instructions for the making of the hydroxmethylbilane synthase.
- PPOX: Protoporphyrinogen oxidase, the gene provides instructions for manufacturing protoporphrinogen oxidate enzymes.
- UROD: Uroporphyrinogen decarboxylase, responsible for the instructions needed to make the enzyme known as uroporphyrinogen.
- UROS: Uroporphyrinogen III synthase, provides instructions on the manufacture of the enzyme called uroporphyrinogen III synthase.
Types Of Porphyrias
There are several different types of porphyrias. There are four types of hepatic porphyrias and these include; doss porphyria (ALA) dehydratase deficiency, acute intermittent porphyria (AIP) porphyria cutanea tarda (PCT), and hereditary coproporphyria (HCP).
Finally, there is variegated porphyria (VP), which is a mixed type of porphyria and transient erthyoporphyria (EEP).