Porphyria

Porphyries: what is it?

Porphyries: where did it come from? What is it exactly ?

The word "Porphyria" comes from "porphyrin", a name that comes from the Greek word for "red pigment".

More specifically, porphyries are the result of the accumulation of porphyrins. In our blood cells, the porphyrins combine with the iron to give the heme, and our blood its beautiful red color.
Porphyrins + iron -> heme.

Heme, by attaching itself to certain proteins, hemoproteins, will allow oxygen to be transported (such as hemoglobin in red blood cells). In the liver, hemoproteins are called cytochromes P450.

Heme and porphyrins are made in all our cells from basic molecules on a synthetic chain, as a car is made with stages, eight in all, each under the responsibility of specific enzyme.

So when there is a defect, a deficiency of an enzyme, in the production line, it happens that porphyrins and / or their precursors accumulate ... and that's the disease!

A breakdown in the assembly line ...

Porphyria are rare genetic diseases caused by the accumulation of porphyrins and / or their precursors ALA and PBG (amino-levulinic acid and porphobilinogen), in one of the two tissues that make the most heme (bone marrow for red blood cell hemoglobin, and liver for cytochrome P450).

When some of the enzymes in the heme synthesis chain are genetically deficient and do only half their work, the porphyrins and / or their two ALA and PBG precursors accumulate.
  • When the precursors ALA and PBG accumulate in the liver, they will cause acute attacks very painful and potentially serious.
  • When porphyrins are produced excessively by the bone marrow or liver, they will accumulate in the skin and cause very characteristic skin lesions.

There are therefore several types of porphyries, each type having different symptoms. The common sign of these different types of porphyria is the presence, in the urine, stool and blood, of a large number of porphyrins and / or their precursors ALA and PBG.

The cause: a genetic mutation!

Porphyries are hereditary genetic diseases. They come from an alteration of the DNA at the level of one of the genes that "codes" for one of the enzymes of the heme synthesis chain. It's a gene that has mutated. And this mutation is inherited.

As you know, our genes come from half our mother, half our father. They are therefore always in duplicate.

  • A genetic disease is called " dominant " if a single mutated gene is necessary to be sick, this is the case of almost all porphyries.
  • The disease will be " recessive " if both copies of the gene are needed to trigger the disease (example of cystic fibrosis and a rare form of porphyria).

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Read also:

> Red blood cells (red blood cells): what is it for?
> Black stools or abnormal color
> Blood in the stool: is it serious?

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