What is porphyria?

The porphyrias are a group of different diseases, each caused by a specific abnormality in the heme production process. Heme is a chemical compound that contains iron and gives blood its red color. The essential functions of heme depend on its ability to bind oxygen. Heme is incorporated into hemoglobin, a protein that enables red blood cells to carry oxygen from the lungs to all parts of the body. Heme also plays a role in the liver where it assists in breaking down chemicals (including some drugs and hormones) so that they are easily removed from the body.

Heme is produced in the bone marrow and liver through a complex process controlled by eight different enzymes. As this production process of heme progresses, several different intermediate compounds (heme precursors) are created and modified. If one of the essential enzymes in heme production is deficient, certain precursors may accumulate in tissues (especially in the bone marrow or liver), appear in excess in the blood, and get excreted in the urine or stool. The specific precursors that accumulate depend on which enzyme is deficient. Porphyria results in a deficiency or inactivity of a specific enzyme in the heme production process, with resulting accumulation of heme precursors.