The genetic condition of Erythropoietic Protoporphyria or EPP is a rare condition that mimics being allergic to the sun. It is not an allergy because the immune system has a severe reaction to the sun. It is caused by a deficiency in an enzyme called ferrochelatase, which leads to high levels of protoporphyrin in the bone marrow, blood plasma, and red blood cells.
Symptoms of EPP are itchy rash on the skin as well as hypersensitivity to sunlight and some artificial light sources such as florescent lighting. After exposure to light, the skin can develop an itchy or burning sensation. The hands, face and arms are the most commonly affected area. Exposure to light through a window will also cause symptoms. Usually, symptoms will subside in 12 to 24 hours and heal without significant scarring. EPP is a very painful disease. Other side effects of this illness are complications with the gall bladder or liver. The symptoms of EPP usually appear in early childhood and will last for life, but because this is such a rare condition, it is difficult to diagnose.
There is no cure for EPP, but there are treatments to manage symptoms. Protection from the sun is the most important. Protective clothing, including broad-brimmed hats, long sleeves, gloves and pants, rather than shorts, is beneficial. Several manufacturers specialize on clothing made of closely woven fabrics for people with photosensitivity. Sun screen does not offer enough protection from the sun and is of little use. Regular monitoring by a physician is necessary to keep track of enzyme levels and other medical issues associated with EPP. Because patients do not have exposure to sunlight, they usually have low levels of Vitamin D and will require supplements.
The July 2 issue of the New England Journal of Medicine published an article about a new synthetic hormone that is in trials now that could make certain skin cells produce more melanin and significantly increases pain-free sun exposure in people with erythropoietic protoporphyria. Two Phase III trials, conducted in Europe and in the United States by researchers at the Icahn School of Medicine at Mount Sinai and six other U.S. sites, showed that the duration of pain-free time in the sun and quality of life were significantly improved by treatment with afamelanotide, a novel synthetic version of a melanocyte-stimulating hormone.