How are the porphyrias classified?
The best way to classify a case of porphyria is to determine which enzyme is deficient, or not functioning properly. Normally these enzymes act in a sequence to make heme from simpler molecules. Heme is a vital substance for all body organs and consists of an iron atom surrounded by a porphyrin molecule. If a specific enzyme is not made properly or there is not enough of the enzyme, it cannot function properly and that step in the heme-making process cannot proceed.
