What is (are) Porphyria ?
Each of the eight types of porphyria corresponds to low levels of a specific enzyme in the heme biosynthetic pathway. Experts often classify porphyrias as acute or cutaneous based on the symptoms a person experiences:
                
- Acute porphyrias affect the nervous system. They occur rapidly and last only a short time.  - Cutaneous porphyrias affect the skin.
                
Two types of acute porphyrias, hereditary coproporphyria and variegate porphyria, can also have cutaneous symptoms.
                
Experts also classify porphyrias as erythropoietic or hepatic:
                
- In erythropoietic porphyrias, the body overproduces porphyrins, mainly in the bone marrow.  - In hepatic porphyrias, the body overproduces porphyrins and porphyrin precursors, mainly in the liver.
                
Table 1 lists each type of porphyria, the deficient enzyme responsible for the disorder, and the main location of porphyrin buildup.
                
Table 1. Types of porphyria
                
Type of Porphyria    Deficient Enzyme    Main Location of Porphyrin Buildup                  delta-aminolevulinate-dehydratase deficiency porphyria    delta-aminolevulinic acid dehydratase    liver        acute intermittent porphyria    porphobilinogen deaminase    liver        hereditary coproporphyria    coproporphyrinogen oxidase    liver        variegate porphyria    protoporphyrinogen oxidase    liver                congenital erythropoietic porphyria    uroporphyrinogen III cosynthase    bone marrow        porphyria cutanea tarda    uroporphyrinogen decarboxylase (~75% deficiency)    liver        hepatoerythropoietic porphyria    uroporphyrinogen decarboxylase (~90% deficiency)    bone marrow        erythropoietic protoporphyria*    ferrochelatase (~75% deficiency)    bone marrow
                
*Protoporphyria XLPP is a variant of erythropoietic protoporphyria.