Erythropoietic Protoporphyria
Erythropoietic protoporphyria is a condition characterized by photosensitivity.
Erythropoietic protoporphyria is the third most common porphyria. It occurs most often in whites but can also occur in people of any origin. Erythropoietic protoporphyria occurs equally in men and women.
In erythropoietic protoporphyria, a deficiency of the enzyme ferrochelatase leads to accumulation of the heme precursor protoporphyrin in the bone marrow, red blood cells, blood plasma, skin, and liver. The enzyme deficiency is usually inherited from one parent.
Accumulation of protoporphyrin in the skin results in extreme sensitivity to sunlight. The sunlight activates the protoporphyrin molecules, which damage the surrounding tissue. Accumulation of protoporphyrins in the liver can cause liver damage. Protoporphyrins in the bile can lead to bile stones.
Symptoms and Diagnosis
Symptoms usually start in childhood. Pain and swelling develop soon after the skin is exposed to sunlight. Because blistering and scarring seldom occur, doctors do not always recognize the disorder. Gallstones cause characteristic abdominal pain (see Section 10, Chapter 140). Liver damage may lead to increasing liver failure, with jaundice and enlargement of the spleen.
Porphyrin levels in urine are not increased. The diagnosis is therefore made when increased levels of protoporphyrin are detected in the plasma and red blood cells.
Prevention and Treatment
Extreme care should be taken to avoid exposure to sunlight. Accidental sun exposure is given the same treatment as is sunburn (see Section 18, Chapter 214). Beta-carotene, when taken in sufficient amounts to cause slight yellowing of the skin, makes many people more tolerant of sunlight; however, sunlight should still be avoided. People who develop gallstones that contain protoporphyrin may need to have them surgically removed. Liver damage, if severe, may necessitate liver transplantation.
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