What are Erythropoietic Protoporphyria and X-Linked Protoporphyria?
EPP and XLP are both protoporphyrias with similar symptoms and similar biochemical findings, but each is caused by a mutation in a different gene. Some people refer to XLP as a “variant form of EPP”. Symptoms usually first occur in early childhood, and include sun sensitivity, marked by severe pain and swelling of sun-exposed areas, but typically with no blistering or scarring. EPP is caused by a deficiency of the enzyme, ferrochelatase (FECH), whereas XLP is due to an increased activity of another enzyme, aminolevulinic acid-synthase 2 (ALAS2). Both result in significant elevations of protoporphyrins in the liver, sometimes resulting in severe liver complications that are difficult to treat and sometimes require liver transplantation. Who gets Erythropoietic Protoporphyria and X-Linked Protoporphyria? EPP and XLP, combined, are the third most common porphyria, with an incidence of possibly 2 to 5 per 1,000,000, and the most common in children. EPP is an autosomal recessive disorder: a
