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. Neither parent has symptoms of CEP, 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 a very rare genetic disorder that affects males and females in equal numbers. Over 200 cases have been reported worldwide.
This disease is extremely rare and is autosomal recessive. Various mutations in the gene for this enzyme have been identified in different families. As is characteristic of the erythropoietic porphyrias, symptoms begin during infancy. Sometimes CEP is recognized as a cause of anemia in a fetus before birth. In less severe cases symptoms may begin during adult life. Porphyrins are markedly increased in bone marrow, red blood cells, plasma, urine and feces. Porphyrins are also deposited in the teeth and bones.
Synonyms of Congenital Erythropoietic Porphyria
- Gunther’s disease
- uroporphyrinogen III synthase deficiency
- UROS deficiency
Mutations in the UROS gene cause CEP. The symptoms of CEP develop due to excessive levels of the specific porphyrins that accumulate in tissues of the body as a result of the markedly impaired function of the UROS enzyme during heme biosynthesis.
Congenital Erythropoietic Porphyria is inherited as an autosomal recessive genetic condition. Recessive genetic disorders occur when an individual inherits two copies of an abnormal gene for the same trait, one from each parent. If an individual receives one normal gene and one gene for the disease, the person will be a carrier for the disease, and usually will not show symptoms. The risk for two carrier parents to both pass the defective gene and have an affected child is 25% with each pregnancy. The risk to have a child who is a carrier like the parents is 50% with each pregnancy. The chance for a child to receive normal genes from both parents and be genetically normal for that particular trait is 25%. The risk is the same for males and females.
Prenatal and preimplantation genetic diagnoses are available for subsequent pregnancies in CEP families.
SIGNS AND SYMPTOMS
Symptoms usually start in infancy or childhood and the diagnosis in most patients is suggested by the reddish color of the urine which stains the diapers. Skin photosensitivity may be extreme, and can lead to blistering, severe scarring and increased hair growth. Bacteria may infect the damaged skin. Facial features and fingers may be lost through phototoxic damage as well as infection. Red blood cells have a shortened life-span, and anemia often results. Synthesis of heme and hemoglobin are actually increased to compensate for the shortened red blood cell survival.
The most common symptom of CEP is hypersensitivity of the skin to sunlight and some types of artificial light (photosensitivity), with blistering of the skin occurring after exposure. Affected individuals may also exhibit abnormal accumulations of body fluid under affected areas (edema) and/or persistent redness or inflammation of the skin (erythema). Affected areas of the skin may develop sac-like lesions (vesicles or bullae), scar, and/or become discolored (hyperpigmentation) if exposure to sunlight is prolonged. These affected areas of skin may become abnormally thick. In addition, in some cases, affected individuals may also exhibit malformations of the fingers and nails. The severity and degree of photosensitivity differ depending on the severity of the patient’s gene lesions which correlate with the deficient enzyme activity. In the great majority of cases, photosensitivity is seen from birth; however, in some cases, it may not occur until childhood, adolescence or adulthood. Patients also have brownish discolored teeth (erythrodontia), which fluoresce under ultraviolet light.
In more severe cases, other symptoms can include a low level of red blood cells (anemia), enlargement of the spleen, and increased hair growth (hypertrichosis). The anemia can be severe and such patients require periodic transfusions to quickly increase the amount of red blood cells and iron in the blood. In severely affected patients, anemia may be present in the fetus. Ocular problems also can occur including corneal scarring, eye inflammation, and infections.
The diagnosis of CEP may be suspected when reddish-colored urine is noted at birth or later in life. This finding, or the occurrence of skin blisters on sun or light exposure, should lead to a thorough clinical evaluation and specialized laboratory tests. The diagnosis can be made by testing the urine for increased levels of specific porphyrins. Diagnostic confirmation is made by measuring the specific (UROS) enzyme activity and/or by identifying the specific lesion(s) in the UROS gene which is/are responsible for the impaired enzyme.
Avoidance of sunlight is essential to prevent the skin lesions in individuals with CEP. The use of topical sunscreens, protective clothing, long sleeves, hats, gloves, and sunglasses are strongly recommended. Individuals with CEP will benefit from window tinting or using vinyls or films to cover the windows in their car or house. Before tinting or shading car windows, affected individuals should check with their local Registry of Motor Vehicles to ensure that such measures do not violate any local codes.
In addition to protection from sunlight, the anemia should be treated, if present. Chronic transfusions have been useful in decreasing the bone marrow production of the phototoxic porphyrins. When successful, bone marrow transplantation has cured patients with CEP, but is accompanied by specific risks of complications and demise.
Blood transfusions and removing the spleen are treatments which may reduce porphyrin production by the bone marrow. Activated charcoal given by mouth is sometimes effective. Stem cell transplantation and gene therapy may also be options in the future.
Referral to an expert porphyria center is recommended for expert diagnosis, care and genetic counseling.
Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. Government funding, and some supported by private industry, are posted on this government web site.