Diseases & Conditions
Erythropoietic protoporphyria is a condition characterized by photosensitivity. The heme precursor protoporphyrin accumulates in the bone marrow and red blood cells. People have severe skin pain and swelling soon after exposure to sunlight. Doctors test blood to look for elevated levels of protoporphyrin. People should avoid exposure to sunlight. Sometimes, beta-carotene can help protect the skin.
Erythropoietic protoporphyria is uncommon. It usually appears in childhood.
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 eventually liver. The enzyme deficiency is inherited from one parent, but in order to develop the disorder people must also inherit a slightly abnormal gene for the enzyme from the other parent.
Accumulation of protoporphyrin in the skin results in extreme sensitivity to sunlight and severe pain after exposure. The sunlight activates the protoporphyrin molecules, which damage the surrounding tissue. Accumulation of protoporphyrins in the liver can cause liver damage. Protoporphyrins excreted in the bile can lead to bile stones.
Symptoms and Diagnosis
Symptoms usually start in childhood. Severe skin pain and swelling develop soon after exposure to sunlight. Because blistering and scarring do not occur, doctors usually do not recognize the disorder. Gallstones cause characteristic abdominal pain (see Gallbladder and Bile Duct Disorders: Gallstones ). Liver damage may lead to increasing liver failure, with jaundice, abdominal pain, and enlargement of the spleen.
Porphyrin levels in urine are not usually increased. The diagnosis is therefore made when increased levels of protoporphyrin are detected in red blood cells.
Did You Know...
Young children often cannot describe their symptoms, so doctors and parents may have difficulty connecting their discomfort to sun exposure.
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 Sunlight and Skin Damage: Sunburn ). Beta-carotene, when taken in sufficient amounts to cause a slight protective 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. Porphyrin accumulation in red blood cells and the condition of the liver should be monitored yearly by testing blood, urine, and stool samples. Liver damage, if severe, may necessitate liver transplantation.
Last full review/revision August 2008 by Stig Thunell, MD, PhD
Source: The Merck Manual Home Edition