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. 
What is (are) Porphyria ?