[Erythropoietic protoporphyria : Clinical manifestations, diagnosis and new therapeutic possibilities].

BACKGROUND

Erythropoietic protoporphyria, the second most common type of the cutaneous porphyrias, is due to an enzymatic deficiency of ferrochelatase, the last enzyme in heme biosynthesis. The enzyme defect leads to an accumulation of protoporphyrin IX in erythrocytes and an elevated excretion of this metabolite in the feces.

METHODS

Usually, disease onset is in early infancy, characterized by increased photosensitivity. During or shortly after sunlight exposure, affected individuals suffer from burning, stinging, itching, and pain in sun-exposed skin areas. These symptoms lead to a considerably reduced quality of life and strict avoidance of sunlight exposure. Subacute symptoms include visible changes like edema and erythema. In the further course of the disease, chronic signs such as lichenification and scarring may occur. A severe complication of hepatic protoporphyrin IX accumulation is the development of a potentially life-threatening fulminant liver failure. Therefore, hepatic laboratory tests and ultrasound of the liver should be performed regularly.

METHODS

Traditionally, therapy merely consisted of consequent photoprotection and orally administered β-carotene. A novel treatment option is afamelanotide (Scenesse®), a synthetic analogue of the naturally occurring α-melanocyte stimulating hormone. Afamelanotide, administered as a subcutaneous implant, induces eumelanin production, independent of preceding UV light exposure. This may enable patients with erythropoietic protoporphyria to stay in sunlight significantly longer than previously possible without complaints, thus, substantially improving quality of life.