EPP

Clinical Features

Most patients experience the onset of photosensitivity before the age of six years and some as early as eighteen months. Patients report, in decreasing order of frequency, burning, swelling, itching and redness of the skin. After severe episodes of photosensitivity, some patients acquire shallow-depressed scars over the nose and cheeks and on the backs of hands. Some patients report only subjective symptoms of itching and burning and have no redness, swelling or scarring; these patients are often dismissed by their physicians as hypochondriacs, when in reality they have EPP.

Thus, it is important for the physician to investigate for the presence of the disease in all patients who report itching and burning of the skin on exposure to light, even in the absence of objective findings.

The amount of exposure to sun that a patient with EPP can tolerate varies from a few minutes to several hours. This photosensitivity is to light in the visible spectrum (400 to 700 nm). These wavelengths are not absorbed by window glass. Therefore, the symptoms can also develop from light passing through glass windows. About half of the patients report decreases in photosensitivity during winter. However, those engaging in skiing report that the light reflected by snow causes severe photosensitivity reactions.

EPP is generally a benign disease. Many patients have somewhat decreased levels of hemoglobin and hematocrit (percentage of the volume of a blood sample occupied by cells). This finding usually requires no treatment. One reported case with severe hemolytic anemia (anemia caused by excessive destruction of red blood cells) improved after splenectomy (removal of the spleen). There also seems to be an increased frequency of cholelithiasis (presence of the formation of solid material in the gall bladder or bile duct), with several patients requiring cholecystectomy (removal of the gall bladder). Chemical analysis of the gallstones reveals high levels of protoporphyrin.

To summarize, in EPP a decreased amount of the enzyme ferrochelatase leads to the accumulation of protoporphyrin in reticulocytes (young red blood cells that appear especially during regeneration of lost blood). This excess protoporphyrin leaks rapidly into the plasma from the maturing reticulocytes and young erythrocytes. The protoporphyrin is then partially cleared from the plasma by the liver and excreted into the bile (with or without some recirculation via the enterohepatic circulation). Accumulation of this protoporphyrin in the liver may lead, in rare cases, to serious liver disease.