Erythropoietic porphyria (EP), or congenital erythropoietic porphyria (CEP), results from a deficiency of an enzyme in the pathway for heme synthesis. This leads to the accumulation of toxic porphyrins, which make tissues photosensitive. The major manifestations are blistering skin conditions, often severe and leading to deformities, and hemolytic anemia. Allogeneic bone marrow transplantation is curative.
Erythropoietic porphyria (EP) belongs to the porphyria group of disorders. These arise from deficiencies in enzymes that catalyze steps in heme biosynthesis. Manifestations of the disease vary and depend on the metabolic intermediates that accumulate and the organs primarily affected. Based on the main organ involved, the porphyria diseases are classified into hepatic and erythroid groups .
EP is a very rare disease that arises because of a deficiency of uroporphyrinogen III synthase. This results in spontaneous formation of type I isomers (uroporphyrinogen I and uroporphyrin I); these are dead-end products, which accumulate mainly in red blood cells, plasma, and bone, and are excreted in urine and feces. Porphyrins are colored, fluoresce in UV light, and cause photosensitivity in biomolecules and damage to tissues.
EP is inherited as an autosomal recessive disorder. Manifestations range from severe cases, detected first as jaundice and pink diaper rash in newborns, or even earlier as intrauterine hydrops due to hemolytic anemia, to milder manifestations in adults.
A characteristic feature of the disease is damage, often severe, to the skin, especially in areas exposed to light (face, hands). There are bullous lesions, which rupture easily and become infected. Repeated damage and infections cause scarring, pigmentation, and thickening of the skin. Epidermal atrophy and destruction of cartilage lead to contractures, loss of digits, and deformities on the face and hands . Hypertrichosis of the face is also common. Damage to the eye  may occur because of several reasons, among which are inflammation and lagophthalmos; scarring of the cornea may lead to visual loss or even blindness. The teeth can have a red color because of deposition of porphyrin in them. Porphyrins can also collect in the bones and cause bone loss and deformities.
Hemolysis, which occurs to varying degrees, is probably because the deposition of uroporphyrin I in erythrocytes renders them fragile. This effect leads to hemolytic anemia, splenomegaly, and thrombocytopenia. Compensatory bone marrow expansion can result in fragile bones .
Children or adults with skin blistering conditions should be tested for EP. Urinary excretion of porphyrins is increased excessively (100-1000 fold) in EP with about 90% being made up of type I isomers . Concentrations of precursors (for example porphobilinogen) are unchanged. Large amounts of porphyrins (mainly coproporphyrins) also appear in the feces. Red blood cells and plasma also contain increased concentrations of porphyrins. Patients with the highest levels of porphyrins are most affected .
Both direct and coupled assays for uroporphyrinogen III synthase activity have been developed . Prenatal diagnosis can be performed by measuring uroporphyrinogen III synthase enzyme activity in chorionic villi or cultured amniotic cells .
Detection of mutations in the synthase gene can also be used for prenatal diagnosis . The mutations in uroporphyrinogen III synthase are heterogeneous, but there is one mutation (C73R) that is present in 40% of cases . Homozygotes for this mutation have the most severe form of the disease; genotype-phenotype correspondence for other mutations has also been examined . In addition to molecular analyses, examination of porphyrin levels should also be undertaken to assess the likely severity of the disease . An elevated concentration of uroporphyrin I in the amniotic fluid is indicative of EP .
Fluorescence microscopy will detect fluorescing nuclei in erythrocyte precursors in EP. Histologic examinations demonstrate cutaneous changes (such as hyalinized walls of blood vessels and caterpillar bodies) that also occur in other porphyrias.