Congenital erythropoietic porphyria (CEP) is a very rare inherited metabolic disorder resulting from the deficient function of the enzyme uroporphyrinogen lll cosynthase (UROS), the fourth enzyme in the heme biosynthetic pathway. Due to the impaired function of this enzyme, excessive amounts of particular porphyrins accumulate, particularly in the bone marrow, plasma, red blood cells, urine, teeth, and bones. The major symptom of this disorder is hypersensitivity of the skin to sunlight and some types of artificial light, such as fluorescent lights (photosensitivity). After exposure to light, the photo-activated porphyrins in the skin cause bullae (blistering) and the fluid-filled sacs rupture, and the lesions often get infected. These infected lesions can lead to scarring, bone loss, and deformities. The hands, arms, and face are the most commonly affected areas. CEP is inherited as an autosomal recessive genetic disorder. Typically, there is no family history of the disease. Both parents are usually healthy, but each carries a defective gene that they can pass to their children. Affected offspring have two copies of the defective gene, one inherited from each parent.
CEP is one of a group of disorders known as the porphyrias. Each porphyria is characterized by abnormally high levels of particular chemicals (porphyrins) in the body due to deficiencies of certain enzymes in the step-wise synthesis of heme, the essential component of hemoglobin and various hemo-proteins. The porphyrias can be classified as cutaneous or acute depending on their respective manifestations (See www.porphyriafoundation.com). There are at least seven types of porphyria. The symptoms associated with the various types of porphyria differ, depending upon the specific enzyme that is deficient. People who have one type of porphyria do not develop the other types, however, rare patients have had two different porphyrias.