Erythropoietic protoporphyria, or EPP, is a rare metabolic disorder which causes severe anaphylactoid reactions to light.
Patients who experience these reactions incur physical burns and ulcers, and are in a state of crisis following only a few minutes of exposure to bright lights, particularly sunlight. These reactions are known as phototoxic reactions.
People living with EPP must avoid sunlight, even reflected light, for life. They are often forced to stay indoors or wear protective clothing as conventional sunscreens have little effect.
As little as a few minutes of natural or artificial light exposure may evoke EPP symptoms.
EPP symptoms can be acute or delayed (subacute). They are most often expressed as:
effusion in tissue
Phototoxicity is unresponsive to traditional pain and burn management techniques, and patients can be incapacitated for days before reactions subside. Most patients withdraw from light exposure in order to manage their phototoxic symptoms.
Approximately 10,000 people globally are affected by EPP, with an estimated 4,000 in the US.