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Erythropoietic protoporphyria (EPP) is a form of porphyria, which varies in severity and can be very painful. It arises from a deficiency in the enzyme ferrochelatase, leading to abnormally high levels of protoporphyrin in the tissue. The severity varies significantly from individual to individual. Both autosomal dominant and autosomal recessive inheritance have been reported with this disorder as has an acquired form of the disease. A clinically similar form of porphyria, known as X-Linked dominant protoporphyria, was identified in 2008. ==Presentation== A common symptom is very painful photosensitivity, manifesting itself as a burning or itching sensation on the surface of the skin, often within a minute of exposure. At times the itching sensations are almost unbearable. Rubbing the affected areas with ice can be the only relief, and that is only temporary. The usual anti-itch remedies, including cortisone anti-histamine topical preparations, and calamine lotion generally provide little or no relief. If a patient presents with a history of anti-itch preparation inefficacy, EPP should be considered. EPP usually first presents in childhood, and most often affects the face and the upper surfaces of the arms, hands, and feet and the exposed surfaces of the legs. Most patients, if the EPP is not as severe, manifest symptoms with onset of puberty when the male and female hormone levels elevate during sexual development and maintenance. More severe EPP can manifest in infancy. Exposure to even indoor light sources can cause the reaction, and the infant, if clothed only in a diaper, will break out everywhere except under the diaper. EPP can be triggered through exposure to sun even though the patient is behind glass. Even the UV emissions from arc welding with the use of full protective mask have been known to trigger EPP. EPP can also manifest between the ages of 3 and 6. EPP is so rare that it has been mentioned on an episode of the popular American TV show House, although it is over-dramatized, and much of the description of EPP is incorrect. Exposure to powerful surgical lights is enough to trigger the reaction. As a precaution, individuals with EPP should tell their close friends and family to make sure that if they ever are taken to the hospital for emergency surgery that the staff be notified of the condition so they can adjust the lighting accordingly. Prolonged exposure to the sun can lead to edema of the hands, face, and feet, rarely with blistering and petechiae. Skin thickening can sometimes occur over time. People with EPP are also at increased risk to develop gallstones. One study has noted that EPP patients suffer from vitamin D deficiency. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Erythropoietic protoporphyria」の詳細全文を読む スポンサード リンク
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