Erythropoietic protoporphyria.

Erythropoietic protoporphyria (EPP) is an inherited photosensitivity disorder producing mild to severe symptoms and attributable to an excessive amount of endogenous protoporphyrin accumulating in body tissues. Following sun exposure, the symptoms are burning pain, edema, erythema, vesicles, and bullare, which at times are hemorrhagic. This condition was first described in 1961. However, some patients previously diagnosed as having solar urticaria, lipoid proteinosis, or hydroa aestivale because of their clinical features ae now known to have EPP. Porphyrins are biochemical intemediates in the synthesis of heme, a moiety that occurs in all living cells and is a basic requirement for aerobic and anaerobic metabolism.