Very Early Diagnosis and Management of Congenital Erythropoietic Porphyria

Congenital erythropoietic porphyria (CEP), a rare form of porphyria, is caused by a defect in the heme biosynthesis pathway of the enzyme uroporphyrinogen III synthase (UROS). Uroporphyrinogen III synthase deficiency leads to an accumulation of nonphysiological porphyrins in bone marrow, red blood cells, skin, bones, teeth, and spleen. Consequently, the exposure to sunlight causes severe photosensitivity, long-term intravascular hemolysis, and eventually, irreversible mutilating deformities. Several supportive therapies such as strict sun avoidance, physical sunblocks, red blood cells transfusions, hydroxyurea, and splenectomy are commonly used in the management of CEP. Currently, the only available curative treatment of CEP is hematopoietic stem cell transplantation (HSCT). In this article, we present a young girl in which precocious genetic testing enabled early diagnosis and allowed curative treatment with HSCT for CEP at the age of 3 months of age, that is, the youngest reported case thus far.

Congenital erythropoietic porphyria: Recent advances

Congenital erythropoietic porphyria (CEP) is a rare autosomal recessive disorder characterized by photosensitivity and by hematologic abnormalities in affected individuals. CEP is caused by mutations in the uroporphyrinogen synthase (UROS) gene. In three reported cases, CEP has been associated with a specific X-linked GATA1 mutation. Disease-causing mutations in either gene result in absent or markedly reduced UROS enzymatic activity. This in turn leads to the accumulation of the non-physiologic and photoreactive porphyrinogens, uroporphyrinogen I and coproporphyrinogen I, which damage erythrocytes and elicit a phototoxic reaction upon light exposure. The clinical spectrum of CEP depends on the level of residual UROS activity, which is determined by the underlying pathogenic loss-of-function UROS mutations. Disease severity ranges from non-immune hydrops fetalis in utero to late-onset disease with only mild cutaneous involvement. The clinical characteristics of CEP include exquisite photosensitivity to visible light resulting in bullous vesicular lesions which, when infected lead to progressive photomutilation of sun-exposed areas such as the face and hands. In addition, patients have erythrodontia (brownish discoloration of teeth) and can develop corneal scarring. Chronic transfusion-dependent hemolytic anemia is common and leads to bone marrow hyperplasia, which further increases porphyrin production. Management of CEP consists of strict avoidance of exposure to visible light with sun-protective clothing, sunglasses, and car and home window filters. Adequate care of ruptured vesicles and use of topical antibiotics is indicated to prevent superinfections and osteolysis. In patients with symptomatic hemolytic anemia, frequent erythrocyte cell transfusions may be necessary to suppress hematopoiesis and decrease marrow production of the phototoxic porphyrins. In severe transfection-dependent cases, bone marrow or hematopoietic stem cell transplantation has been performed, which is curative. Therapeutic approaches including gene therapy, proteasome inhibition, and pharmacologic chaperones are under investigation.

CRISPR-Cas9 genome editing induces megabase-scale chromosomal truncations

CRISPR-Cas9 is a promising technology for genome editing. Here we use Cas9 nuclease-induced double-strand break DNA (DSB) at the UROS locus to model and correct congenital erythropoietic porphyria. We demonstrate that homology-directed repair is rare compared with NHEJ pathway leading to on-target indels and causing unwanted dysfunctional protein. Moreover, we describe unexpected chromosomal truncations resulting from only one Cas9 nuclease-induced DSB in cell lines and primary cells by a p53-dependent mechanism. Altogether, these side effects may limit the promising perspectives of the CRISPR-Cas9 nuclease system for disease modeling and gene therapy. We show that the single nickase approach could be safer since it prevents on- and off-target indels and chromosomal truncations. These results demonstrate that the single nickase and not the nuclease approach is preferable, not only for modeling disease but also and more importantly for the safe management of future CRISPR-Cas9-mediated gene therapies.

[Erythropoietic protoporphyria. A rare inherited metabolic disorder with skin symptoms]

Erythropoietic protoporphyria (EPP) is a rare inherited metabolic disorder, resulting from a deficiency of a specific enzyme, ferrochelatase, in the haem biosynthesis pathway. Early and late skin symptoms in EPP are demonstrated by three case stories. Diagnosis depends on characteristic skin symptoms and raised level of protoporphyrin in erythrocytes. The cases illustrate the aspect of inheritance, prophylaxis and recommended follow-up in EPP.

Allogeneic bone marrow transplantation in a 7-year-old girl with congenital erythropoietic porphyria: a treatment dilemma

Congenital erythropoietic porphyria (CEP, Günther's disease) has a very variable phenotype. In the more severely affected, bone marrow transplantation (BMT) is potentially curative, but is not without risks. We describe a 7-year-old girl with CEP characterized by severe photosensitivity but only mild anaemia, in whom the difficult decision to proceed with allogeneic BMT was made after discussion in a multidisciplinary team. She has shown successful engraftment, accompanied by biochemical and clinical resolution of her metabolic disease. She remains well 3 years later, the oldest patient with CEP receiving BMT to survive beyond 12 months. However, she has experienced significant morbidity including florid cutaneous graft-versus-host disease with postinflammatory hypopigmentation. Her case is important in highlighting the delay in diagnosis not uncommon in this condition and the complex decision-making process involved in proceeding with BMT.

Modern diagnosis and management of the porphyrias

Recent advances in the molecular understanding of the porphyrias now offer specific diagnosis and precise definition of the types of genetic mutations involved in the disease. Molecular diagnostic testing is powerful and very useful in kindred evaluation and genetic counselling when a disease-responsible mutation has been identified in the family. It is also the only way to properly screen asymptomatic gene carriers, facilitating correct treatment and appropriate genetic counselling of family members at risk. However, it should be noted that DNA-based testing is for the diagnosis of the gene carrier status, but not for the diagnosis of clinical syndrome or severity of the disease, e.g. an acute attack. For the diagnosis of clinically expressed porphyrias, a logical stepwise approach including the analysis of porphyrins and their precursors should not be underestimated, as it is still very useful, and is often the best from the cost-effective point of view.

Two brothers with mild congenital erythropoietic porphyria due to a novel genotype

BACKGROUND

Congenital erythropoietic porphyria (CEP) is a rare autosomal recessive disease caused by the deficient activity of the heme biosynthetic enzyme, uroporphyrinogen III synthase (URO-synthase), and the accumulation of the nonphysiologic and phototoxic porphyrin I isomers. Clinical manifestations range from severe mutilation to mild erosions and blisters on sun-exposed areas. Evaluation of the URO-synthase mutation and residual enzyme activity has been correlated with the phenotypic expression of the disease.

OBSERVATIONS

We describe 16- and 4-year-old brothers with CEP with a mild phenotype due to a novel genotype, one allele having a promoter mutation (-76G-->A) and the other having an exonic missense mutation (G225S). The father and a 4-year-old fraternal twin brother were carriers of the -76G-->A mutation, whereas the mother and a 15-year-old brother were carriers of the G225S mutation. Previous in vitro expression studies demonstrated that the G225S mutation severely decreased URO-synthase activity to 1.2% of normal, whereas the promoter mutation decreased the activity to approximately 50% of wild type, accounting for the mild clinical phenotype.

CONCLUSION

The mild disease phenotype in these patients is a further example of the clinical heterogeneity seen in CEP and is additional proof that in vitro enzyme expression studies provide dependable genotype-phenotype correlations.

A knock-in mouse model of congenital erythropoietic porphyria

Congenital erythropoietic porphyria (CEP) is a recessive autosomal disorder characterized by a deficiency in uroporphyrinogen III synthase (UROS), the fourth enzyme of the heme biosynthetic pathway. The severity of the disease, the lack of specific treatment except for allogeneic bone marrow transplantation, and the knowledge of the molecular lesions are strong arguments for gene therapy. An animal model of CEP has been designed to evaluate the feasibility of retroviral gene transfer in hematopoietic stem cells. We have previously demonstrated that the knockout of the Uros gene is lethal in mice (Uros(del) model). This work describes the achievement of a knock-in model, which reproduces a mutation of the UROS gene responsible for a severe UROS deficiency in humans (P248Q missense mutant). Homozygous mice display erythrodontia, moderate photosensitivity, hepatosplenomegaly, and hemolytic anemia. Uroporphyrin (99% type I isomer) accumulates in urine. Total porphyrins are increased in erythrocytes and feces, while Uros enzymatic activity is below 1% of the normal level in the different tissues analyzed. These pathological findings closely mimic the CEP disease in humans and demonstrate that the Uros(mut248) mouse represents a suitable model of the human disease for pathophysiological, pharmaceutical, and therapeutic purposes.

Successful match-unrelated donor bone marrow transplantation for congenital erythropoietic porphyria (Günther disease)

Congenital erythropoietic porphyria (CEP; Gunther disease; OMIM 263700) is a rare autosomal recessive disorder caused by a deficiency of uroporphyrinogen III synthase (UROS). The deficiency of this enzyme is associated with lifelong overproduction of series I porphyrins which circulate and are deposited in many tissues, causing light-sensitisation and severe damage to skin beginning in childhood. Blistering and scarring of exposed areas may lead to mutilating deformities. We describe two cases: a 4-year-old boy and his first cousin who were cured of CEP by matched unrelated donor bone marrow transplants. Both are alive and disease-free 3 and 2 years post-transplant, respectively. Cutaneous lesions improved dramatically. The correction of the enzyme deficiency was confirmed by measuring erythrocyte UROS activity and urinary porphyrin excretion. Chimerism was complete for both children. Both patients were homoallelic for a novel mutation of the UROS gene, the missense mutation A69T.

CONCLUSION

Considering the severity of the disease, if HLA-matched sibling donor is not available, haematopoietic stem cell transplantation using a matched unrelated donor should be strongly considered for treating congenital erythropoietic porphyria since this is currently the only known curative therapy.

The prenatal presentation of congenital erythropoietic porphyria: report of two siblings with elevated maternal serum alpha-fetoprotein

Congenital erythropoietic porphyria (CEP), also termed Günther's disease, is extremely rare and is inherited as an autosomal recessive trait. The mutation that causes the most severe deficiency of the enzyme uroporphyrinogen III synthase (URO-synthase) is C73R. Inheritance of two abnormal alleles results in the accumulation of porphyrins of isomer type I that are biologically useless but cause a wide spectrum of abnormalities in multiple organs. The intrauterine diagnosis of the first affected conceptus within a family is extremely challenging despite abnormal ultrasound findings suggesting severe fetal anemia. We report the abnormal findings in a pair of successive pregnancies in a single Caucasian family that yielded two C73R homozygous affected offspring. The course of the pregnancies, sonographic and laboratory abnormalities, method used for intrauterine diagnosis, therapeutic interventions, and variability of outcome between cases within a single family and the difficulty in managing even prenatally diagnosed cases are reported and discussed.

Diagnosis and management of the erythropoietic porphyrias

The erythropoietic porphyrias are erythropoietic protoporphyria, and congenital erythropietic porphyria. Diagnosis is made based on clinical manifestations, and their characteristic porphyrin profiles. There are multiple treatment options for these two porphyrias, however, aside from bone marrow transplant for CEP, none is curative.

Lentivirus-mediated gene transfer of uroporphyrinogen III synthase fully corrects the porphyric phenotype in human cells

Congenital erythropoietic porphyria (CEP) is an inherited disease due to a deficiency in the uroporphyrinogen III synthase, the fourth enzyme of the heme biosynthesis pathway. It is characterized by accumulation of uroporphyrin I in the bone marrow, peripheral blood and other organs. The prognosis of CEP is poor, with death often occurring early in adult life. For severe transfusion-dependent cases, when allogeneic cell transplantation cannot be performed, the autografting of genetically modified primitive/stem cells may be the only alternative. In vitro gene transfer experiments have documented the feasibility of gene therapy via hematopoietic cells to treat this disease. In the present study lentiviral transduction of porphyric cell lines and primary CD34(+) cells with the therapeutic human uroporphyrinogen III synthase (UROS) cDNA resulted in both enzymatic and metabolic correction, as demonstrated by the increase in UROS activity and the suppression of porphyrin accumulation in transduced cells. Very high gene transfer efficiency (up to 90%) was achieved in both cell lines and CD34(+) cells without any selection. Expression of the transgene remained stable over long-term liquid culture. Furthermore, gene expression was maintained during in vitro erythroid differentiation of CD34(+) cells. Therefore the use of lentiviral vectors is promising for the future treatment of CEP patients by gene therapy.

Congenital erythropoietic porphyria: dilemmas in present day management

Congenital erythropoietic porphyria is a rare autosomal recessive disorder of haem biosynthesis caused by a deficiency of uroporphyrinogen III synthetase. There is resultant accumulation and hyperexcretion of porphyrinogens of the isomer I variety. These are converted by spontaneous oxidation into their corresponding photoactive porphyrins leading to photodamage. Accumulation of porphyrins results in haemolysis and extensive photosensitivity. The consequences of chronic haemolysis are splenomegaly, reactive erythroid hyperplasia, erythrodontia, bone fragility, extreme photosensitivity and photomutilation. We present a 35-year-old man who has the severe infantile form and illustrates the haematological and photodestructive complications despite attempts at treatment with hypertransfusion, oral charcoal therapy and beta-carotene. Allogenic bone marrow transplantation has been considered but because of the high associated mortality this procedure has been discounted at present in the management of our patient.

Acute scleritis as a manifestation of congenital erythropoietic porphyria

PURPOSE

To report a case of congenital erythropoietic porphyria that presented as acute scleritis over a bilateral scleromalacia perforans in the interpalpebral fissure.

METHODS

An 18-year-old man presented with painful red eye, a history of photophobia, and passing highly colored urine since childhood. Dermatological and biochemical evaluations were done.

RESULTS

The patient had normal vision in both eyes with bilateral scleromalacia perforans. The right eye showed painful, nodular scleritis. Dermatological examination revealed multiple, vesciculobullous cutaneous lesions with atrophy and pseudoscleroderma changes, hypertrichosis, and bluish discoloration of teeth. Immunofluorescent microscopy of fresh peripheral smear showed brilliant red fluorescence of erythrocytes. Spectroscopic analysis of urine revealed excretion of porphyrin, thus confirming a diagnosis of congenital erythropoietic porphyria. The patient's condition improved with local and systemic steroid therapy along with general photoprotective measures for the exposed parts of the body.

CONCLUSION

Acute scleritis could be the presenting feature in a rare case of congenital erythropoietic porphyria, warranting systemic evaluation.

Treatment of severe congenital erythropoietic porphyria by bone marrow transplantation

Congenital erythropoietic porphyria (CEP), which is the result of a deficiency of uroporphyrinogen (URO) III synthase activity, is the most disfiguring porphyria in humans. Various methods of treatment have been used to treat CEP with varying success, including erythrocyte transfusion, hydroxyurea, and splenectomy. The only treatment that corrects the enzymatic defect resulting in a cure is bone marrow/stem cell transplantation, which has been reported previously in only 5 patients worldwide. We describe the first patient with CEP who underwent successful bone marrow transplantation performed in the United States and review the therapeutic options in the management of this challenging type of porphyria.

Correction of deficient CD34+ cells from peripheral blood after mobilization in a patient with congenital erythropoietic porphyria

Congenital erythropoietic porphyria (CEP) is an inherited disease due to a deficiency in the uroporphyrinogen III synthase (UROS), the fourth enzyme of the heme pathway. It is characterized by accumulation of uroporphyrin I in the bone marrow, peripheral blood, and other organs. The onset of most cases occurs in infancy and the main symptoms are cutaneous photosensitivity and hemolysis. For severe transfusion-dependent cases, when allogeneic cell transplantation cannot be performed, autografting of genetically modified primitive/stem cells is the only alternative. In the present study, efficient mobilization of peripheral blood primitive CD34(+) cells was performed on a young adult CEP patient. Retroviral transduction of this cell population with the therapeutic human UROS (hUS) gene resulted in both enzymatic and metabolic correction of CD34(+)-derived cells, as demonstrated by the increase in UROS activity and by a 53% drop in porphyrin accumulation. A 10-24% gene transfer efficiency was achieved in the most primitive cells, as demonstrated by the expression of enhanced green fluorescent protein (EGFP) in long-term culture-initiating cells (LTC-IC). Furthermore, gene expression remained stable during in vitro erythroid differentiation. Therefore, these results are promising for the future treatment of CEP patients by gene therapy.

Treatment of congenital erythropoietic porphyria in children by allogeneic stem cell transplantation: a case report and review of the literature

Congenital erythropoietic porphyria (CEP) is a rare autosomal recessive disorder of porphyrin metabolism in which the genetic defect is the deficiency of uroporphyrinogen III cosynthase (UIIIC). Deficiency of this enzyme results in an accumulation of high amounts of uroporphyrin I in all tissues leading to hemolytic anemia, splenomegaly, erythrodontia, bone fragility, exquisite photosensitivity and mutilating skin lesions. We describe the case of a 23-month-old boy who was cured of his CEP by a matched-sibling allogeneic bone marrow transplant, and review the published clinical experience regarding transplantation in this disease. He is alive and disease-free 15 months post transplant. All of his disease manifestations except for the erythrodontia have resolved. His UIIIC level and stool and erythrocyte porphyrin metabolites have almost completely corrected. He is the sixth child reported to be cured of this disease by stem cell transplantation, five cases being long-term survivors. If patients with this disease have an HLA-matched sibling, then stem cell transplantation should be strongly considered because this is currently the only known curative therapy.

Erythropoietic and hepatic porphyrias

Porphyrias are divided into erythropoietic and hepatic manifestations. Erythropoietic porphyrias are characterized by cutaneous symptoms and appear in early childhood. Erythropoietic protoporphyria is complicated by cholestatic liver cirrhosis and progressive hepatic failure in 10%, of patients. Acute hepatic porphyrias (delta-aminolaevulinic acid dehydratase deficiency porphyria, acute intermittent porphyria, hereditary coproporphyria and variegate porphyria) are characterized by variable extrahepatic gastrointestinal, neurological-psychiatric and cardiovascular manifestations requiring early diagnosis to avoid life-threatening complications. Acute hepatic porphyrias are pharmacogenetic and molecular regulatory diseases (without porphyrin accumulation) mainly induced by drugs, sex hormones, fasting or alcohol. The disease process depends on the derepression of hepatic delta-aminolaevulinic acid synthase following haem depletion. In contrast to the acute porphyrias, nonacute, chronic hepatic porphyrias such as porphyria cutanea tarda are porphyrin accumulation disorders leading to cutaneous symptoms associated with liver disease, especially caused by alcohol or viral hepatitis. Alcohol, oestrogens, haemodialysis, hepatitis C and AIDS are triggering factors. Porphyria cutanea tarda is the most common porphyria, followed by acute intermittent porphyria and erythropoietic protoporphyria. The molecular genetics of the porphyrias is very heterogenous. Nearly every family has its own mutation. The mutations identified account for the corresponding enzymatic deficiencies, which may remain clinically silent throughout life. Thus, the recognition of the overt disorder with extrahepatic manifestations depends on the demonstration of biochemical abnormalities due to these primary defects and compensatory hepatic overexpression of hepatic delta-aminolaevulinic acid synthase in the acute porphyrias. Consequently, haem precursors are synthesized in excess. The increased metabolites upstream of the enzymatic defect are excreted into urine and faeces. The diagnosis is based on their evaluation. Primary enzymatic or molecular analyses are noncontributary and may be misleading. Acute polysymptomatic exacerbations accompany a high excretory constellation of porphyrin precursors delta-aminolaevulinic acid and porphobilinogen. Homozygous or compound heterozygous variants of acute hepatic porphyrias may already manifest in childhood.

Reversion of hepatobiliary alterations By bone marrow transplantation in a murine model of erythropoietic protoporphyria

Erythropoietic protoporphyria (EPP) is characterized clinically by cutaneous photosensitivity and biochemically by the accumulation of excessive amounts of protoporphyrin in erythrocytes, plasma, feces, and other tissues, such as the liver. The condition is inherited as an autosomal dominant or recessive trait, with a deficiency of ferrochelatase activity. A major concern in EPP patients is the development of cholestasis with accumulation of protoporphyrin in hepatobiliary structures and progressive cellular damage, which can rapidly lead to fatal hepatic failure. The availability of a mouse model for the disease, the Fech(m1Pas)/Fech(m1Pas) mutant mouse, allowed us to test a cellular therapy protocol to correct the porphyric phenotype. When Fech/Fech mice received bone marrow cells from normal animals, the accumulation of protoporphyrin in red blood cells and plasma was reduced 10-fold but still remained 2.5 times above normal levels. Interestingly, in very young animals, bone marrow transplantation can prevent hepatobiliary complications as well as hepatocyte alterations and partially reverse protoporphyrin accumulation in the liver. Bone marrow transplantation may be an option for EPP patients who are at risk of developing hepatic complications.

Fluorescence-based selection of retrovirally transduced cells in congenital erythropoietic porphyria: direct selection based on the expression of the therapeutic gene

BACKGROUND

Congenital erythropoietic porphyria (CEP) is an inherited disease caused by a deficiency of uroporphyrinogen III synthase, the fourth enzyme of the haem biosynthesis pathway. It is characterized by accumulation of uroporphyrin I in the bone marrow, peripheral blood and other organs. The prognosis of CEP is poor with death occurring in early adult life and available treatments are only symptomatic and unsatisfactory. In vitro gene transfer experiments have documented the feasibility of gene therapy via haematopoietic stem cells to treat this disease. To facilitate future ex vivo gene therapy in humans, the design of efficient selection procedures to increase the frequency of genetically corrected cells prior to autologous transplantation is a critical step.

METHODS

An alternative selection procedure based upon expression of a transferred gene was performed on a lymphoblastoid (LB) cell line from a patient with congenital erythropoietic porphyria to obtain high frequencies of genetically modified cells. The presence of exogeneous delta-aminolevulinic acid (ALA), a haem precursor, induces an increase in porphyrin accumulation in LB deficient cells. Porphyrins exhibit a specific fluorescent emission and can be detected by cytofluorimetry under ultraviolet excitation.

RESULTS

In genetically modified cells, the restored metabolic flow from ALA to haem led to a lesser accumulation of porphyrins in the cells, which were easily separated from the deficient cells by flow cytometry cell sorting.

CONCLUSION

This selection process represents a rapid and efficient procedure and an excellent alternative to the use of potentially harmful gene markers in retroviral vectors.

The cutaneous porphyrias: a review. The British Photodermatology Group

Many patients with cutaneous porphyria have curable or controllable disease; untreated porphyria may prove fatal. The genetic defects and mechanisms underlying porphyria are steadily being delineated, treatments have become more appropriate and genetic counselling is now more accurate. A summary of the basic diagnostic features, management and recent advances in the cutaneous porphyrias is presented, based on a workshop held by the British Photodermatology Group.

Congenital erythropoietic porphyria: a case report

Congenital erythropoietic porphyria is a rare autosomal recessive disorder of heme synthesis resulting from deficiency of uroporphyrinogen III synthase (UROIIIS). It is the most severe porphyria. The clinical manifestations are markedly variable due to the different mutation in the UROIIIS gene. We recently diagnosed a case of congenital erythropoietic porphyria. A 9-year-old boy presented with recurrent ulcers on the skin especially dorsum of the hands and feet since aged 3. The physical examination revealed ulcers on the dorsum of the feet, mutilation of the fingers, fluorescent erythrodontia, and darkening and hypertrichosis of the sun exposed area. Laboratory findings showed mild hemolysis, red urine, increased serum alkaline phosphatase level, and fluorescence of the red blood cell and urine. The histopathology was consistent with porphyria. The urine and plasma porphyrin levels confirmed the diagnosis of congenital erythropoietic porphyria. The administration of oral ultracarbon and topical zinc oxide has been tried.

Congenital erythropoietic porphyria successfully treated by allogeneic bone marrow transplantation

The long-term biochemical and clinical effectiveness of allogenic bone marrow transplantation (BMT) was shown in a severely affected, transfusion-dependent 18-month-old female with congenital erythropoietic porphyria (CEP), an autosomal recessive inborn error of heme biosynthesis resulting from mutations in the uroporphyrinogen III synthase (URO-synthase) gene. Three years post-BMT, the recipient had normal hemoglobin, markedly reduced urinary porphyrin excretion, and no cutaneous lesions with unlimited exposure to sunlight. The patient was homoallelic for a novel URO-synthase missense mutation, G188R, that expressed less than 5% of mean normal activity in Escherichia coli, consistent with her transfusion dependency. Because the clinical severity of CEP is highly variable, ranging from nonimmune hydrops fetalis to milder, later onset forms with only cutaneous lesions, the importance of genotyping newly diagnosed infants to select severely affected patients for BMT is emphasized. In addition, the long-term effectiveness of BMT in this patient provides the rationale for future hematopoietic stem cell gene therapy in severely affected patients with CEP.

Congenital erythropoietic porphyria

Congenital erythropoietic porphyria (CEP) is one of the rarest autosomal-recessive disorders of the porphyrin metabolism caused by the homozygous defect of uroporphyrinogen III cosynthase. High amounts of uroporphyrin I accumulate in all cells and tissues, reflected by an increased erythrocyte porphyrin concentration and excretion of high porphyrin amounts in urine and feces. Dermal deposits of uroporphyrin frequently induce a dramatic phototoxic oxygen-dependent skin damage with extensive ulcerations and mutilations. Splenomegaly and hemolytic anemia are typical internal symptoms. Skeletal changes such as osteolysis and calcifications are frequent. Up to date 130 cases of CEP have been published. Splenectomy and erythrocyte transfusions showed some beneficial effect. Bone marrow transplantation was performed in 3 patients and stem cell transplantation in 1. The best therapy is the avoidance of sunlight. We give a report on our latest cases of CEP.

Porphyrins in urine, plasma, erythrocytes, bile and faeces in a case of congenital erythropoietic porphyria (Gunther's disease) treated with blood transfusion and iron chelation: lack of benefit from oral charcoal

Congenital erythropoietic porphyria is a rare genetic disorder in which deficiency of uroporphyrinogen III synthase results in excessive production of Type I porphyrins. The main clinical features are severe photodestruction of the skin and haemolytic anaemia. Treatment consists of shielding from light, blood transfusions and splenectomy, but is generally unsatisfactory. Previous studies have suggested that oral charcoal may be of benefit by binding porphyrins in the gut. A trial was therefore undertaken to evaluate this possibility. Porphyrins in urine, plasma and erythrocytes were measured by HPLC in a 23-year-old male patient with congenital erythropoietic porphyria, during an 8 week "run-in" period, and for a further 3 weeks when oral charcoal was given. Total urinary porphyrin excretion was 79-283 mumol/24 h consisting of 75% uroporphyrin I, 15% coproporphyrin I and smaller amounts of hepta-, hexa-, and pentacarboxylic porphyrins. Similar proportions were found in plasma and erythrocytes. During the first 24 h of charcoal administration a minor decrease in plasma and erythrocyte porphyrins was detected but this was not maintained during the remainder of the trial. In bile and faeces coproporphyrin I constituted approximately 95% of the porphyrins, with 2-3% coproporphyrin III and smaller amounts of pentaporphyrins I and III, but only trace amounts of uroporphyrin I. Oral charcoal was of no value in this case. Reasons are discussed in the context of biochemical differences between this patient with classical Gunther's disease and the similar clinical syndrome due to deficiency of uroporphyrinogen decarboxylase.

Congenital erythropoietic porphyria: prolonged high-level expression and correction of the heme biosynthetic defect by retroviral-mediated gene transfer into porphyric and erythroid cells

Congenital erythropoietic porphyria (CEP) is an autosomal recessive disorder resulting from the deficient activity of the heme biosynthetic enzyme uroporphyrinogen III synthase (UROS). Severely affected patients are transfusion dependent and have mutilating cutaneous manifestations. Successful bone marrow transplantation has proven curative, providing the rationale for stem cell gene therapy. Toward this goal, two retroviral MFG vectors containing the UROS cDNA were constructed, one with the wild-type sequence (MFG-UROS-wt) and a second with an optimized Kozak consensus sequence (MFG-UROS-K). Following transduction of CEP fibroblasts, the MFG-UROS-wt and MFG-UROS-K vectors increased the endogenous activity without selection to levels that were 18- and 5-fold greater, respectively, than the mean activity in normal fibroblasts. Notably, the MFG-UROS-wt vector expressed UROS activity in CEP fibroblasts at these high levels for over 6 months without cell toxicity. Addition of either delta-aminolevulinic acid (ALA) or ferric chloride did not affect expression of the transduced UROS gene nor did the increased concentrations of uroporphyrin isomers or porphyrin intermediates affect cell viability. Similarly, transduction of CEP lymphoblasts with the MFG-UROS-wt vector without G418 selection increased the endogenous UROS activity by 7-fold or almost 2-fold greater than that in normal lymphoblasts. Transduction of K562 erythroleukemia cells by cocultivation with the MFG-UROS-wt producer cells increased their high endogenous UROS activity by 1.6-fold without selection. Clonally isolated K562 cells expressed UROS for over 4 months at mean levels 4.7-fold greater than the endogenous activity without cell toxicity. Thus, the prolonged, high-level expression of UROS in transduced CEP fibroblasts and lymphoblasts, as well as in transduced K562 erythroid cells, demonstrated that the enzymatic defect in CEP cells could be corrected by retroviral-mediated gene therapy without selection and that the increased intracellular porphyrin intermediates were not toxic to these cells, even when porphyrin production was stimulated by supplemental ALA or iron. These in vitro studies provide the rationale for ex vivo stem cell gene therapy in severely affected patients with CEP.

Molecular genetics of congenital erythropoietic porphyria

Congenital erythropoietic porphyria (CEP), an autosomal recessive inborn error of heme biosynthesis, results from the markedly deficient activity of the cytosolic enzyme, uroporphyrinogen III synthase (URO-synthase). The accumulation of the nonphysiological and pathogenic porphyrin isomers, uroporphyrin I and coproporphyrin I, leads to the clinical manifestations of CEP. Disease severity in unrelated patients is markedly heterogeneous, ranging from fetal demise or severe transfusion dependency throughout life to milder adult cases with only cutaneous photosensitivity. To date, 18 mutations causing CEP have been described in the URO-synthase gene, including single base substitutions, insertions and deletions, and splicing defects. Most mutations have been identified in one or a few unrelated families with the exception of C73R, L4F, and T228M which occurred in about 33%, 8%, and 7% of the mutant alleles studied, respectively. Prokaryotic expression of the mutant URO-synthase alleles identified those with significant residual activity, thereby permitting genotype/phenotype predictions for severe to milder phenotypes of this clinically heterogeneous disease. As successful bone marrow transplantation in severely affected patients has proven curative, current efforts are underway to develop hematopoietic stem cell gene therapy for CEP.

[Allogeneic bone marrow transplantation in congenital erythropoietic porphyria. Gunther's disease]

INTRODUCTION

The congenital erythropoietic porphyria (Günther's disease) (CEP) is a rare autosomal recessively metabolic disease due to the deficit of uroporphyrinogen III cosynthetase, fourth enzyme of the porphyrin-heme biosynthesis. This disease is characterized by severe cutaneous photosensitivity with profound skin lesions, hemolytic anemia and excess of uroporphyrin I excretion. The vital prognosis is very bad and until now, no treatment seems to be efficient. Bone marrow transplantation seems to be able to correct the enzymatic deficit that causes the disease because it is located in the bone marrow.

OBSERVATION

We report the case of a four and a half year old girl who received an allogeneic bone marrow transplantation (BMT) at the age of two. Despite an encouraging result, the first transplantation failed. A second allogeneic transplantation was attempted eight months later with the same HLA identical heterozygous donor and bone marrow engrafment succeeded. Twenty one months after the second bone marrow transplantation, clinical and biological results are still excellent.

DISCUSSION

No classical treatment of CEP really proved its efficiency and no one was curative. CEP resulting from an homozygous deficiency in uroporphyrinogen III cosynthetase, enzyme that takes part in the porphyrin-heme biosynthesis which is principally located in the erythropoietic system of the bone marrow, substitution of this defective lineage by BMT was a very attractive treatment to correct this anomaly. The first bone marrow transplantation attempted on an affected child in 1990 in Manchester failed because the patient died of infections complications. After the failure of the first transplantation, our little patient is now healed twenty one months after the second BMT and biochemical anomalies are corrected. If a long follow up is necessary to appreciate the long-term efficiency of this treatment, allogenic bone marrow transplantation seems to cure Günther's disease and must be proposed as the treatment of this affection.

Gene transfer of the uroporphyrinogen III synthase cDNA into haematopoietic progenitor cells in view of a future gene therapy in congenital erythropoietic porphyria

Congenital erythropoietic porphyria (CEP) is an inherited metabolic disorder characterized by an overproduction and accumulation of porphyrins in bone marrow. This autosomal recessive disease results from a deficiency of uroporphyrinogen III synthase (UROIIIS), the fourth enzyme of the haem biosynthetic pathway. It is phenotypically heterogeneous: patients with mild disease have cutaneous involvement, while more severely affected patients are transfusion dependent. The cloning of UROIIIS cDNA and genomic DNA has allowed the molecular characterization of the genetic defect in a number of families. To date, 22 different mutations have been characterized. Allogeneic bone marrow transplantation is the only curative treatment available for the severe, transfusion-dependent, cases. When bone marrow transplantation cannot be performed owing to the absence of a suitable donor, the autografting of genetically modified cells is an appealing alternative. The best approach to somatic gene therapy in this disease involves the use of recombinant retroviral vectors to transduce cells ex vivo, followed by autologous transplantation of the genetically modified cells. We investigated retroviral transfer in deficient human fibroblasts, immortalized lymphoblasts as well as bone marrow cells, and obtained a complete restoration of the enzymatic activity and full metabolic correction. Using K562 cells, an erythroleukaemic cell line, the expression of the transgene remained stable during 3 months and during erythroid differentiation of the cells. Finally, a 1.6- to 1.9-fold increase in enzyme activity compared to the endogenous level was found in normal CD34+ cells, a population of heterogeneous cells known to contain the progenitor/stem cells for long-term expression. The future availability of a mouse model of the disease will permit ex vivo gene therapy experiments on the entire animal.

Congenital erythropoietic porphyria

Congenital erythropoietic porphyria is a rare autosomal-recessive disorder of the porphyrin metabolism caused by the homozygous defect of uroporphyrinogen III cosynthase. High amounts of uroporphyrin I accumulate in all cells and tissues, reflected by an increased erythrocyte porphyrin concentration and excretion of high porphyrin amounts in urine and feces. Dermal deposits of uroporphyrin frequently induce a dramatic phototoxic oxygen-dependent skin damage with extensive ulcerations and mutilations. Splenomegaly and hemolytic anemia are typical internal symptoms. Skeletal changes such as osteolysis and calcifications are frequent. To date 130 cases of congenital erythropoietic porphyria have been published and are summarized here. Splenectomy, erythrocyte transfusions, and bone marrow transplantation have shown some beneficial effect. The best therapy is the avoidance of sunlight. In the two patients with congenital erythropoietic porphyria described here, oral administration of the oxygen quenchers ascorbic acid and alpha-tocopherol resulted in an improvement in the reduced hemoglobin and erythrocyte concentrations.

[A model of congenital erythropoietic porphyria for gene transfer in hematopoietic cells]

CEP is a rare disease inherited as an autosomal recessive trait and characterized by an overproduction and accumulation of porphyrins in the bone-marrow. Because the predominant site of metabolic expression of the disease is the erythropoietic system, bone marrow transplantation represents a curative treatment for patients with severe phenotypes. This treatment can be considered in severe cases when the disease appears in the first few years of life. When bone marrow transplantation is not possible, gene therapy by transplantation of genetically modified hematopoietic cells is an attractive alternative for the future. In this report, we present the restoration of enzymatic activity and the metabolic correction of deficient cells in vitro after transduction with retroviral vectors. The future availability of a mouse model of the disease will permit ex vivo gene therapy experiments on the entire animal.

Correction of congenital erythropoietic porphyria by bone marrow transplantation

Congenital erythropoietic porphyria (Gunther disease) is a rare metabolic disorder caused by uroporphyrinogen III synthetase deficiency. We report the case of a 2-year-old girl with a severe form of this disease who received HLA-identical bone marrow transplantation from her heterozygous sister. Two transplantations were necessary to obtain full hematopoietic chimerism. Correction of the enzyme deficiency was confirmed by measuring erythrocyte uroporphyrinogen III synthetase activity. The patient's clinical condition improved dramatically, and she is well 1 year after the second transplantation, with no further treatment. Although long-term efficacy remains to be confirmed, we conclude that allogeneic bone marrow transplantation can cure patients with congenital erythropoietic porphyria.

Successful cord blood stem cell transplantation for congenital erythropoietic porphyria (Gunther's disease)

Congenital erythropoietic porphyria (Gunther's disease, GD) is a rare autosomal recessive disease. It results from the deficiency of uroporphyrinogen III synthase, the fourth enzyme on the metabolic pathway of heme synthesis. GD leads to severe scarring of the face and hands as a result of photosensitivity and fragility of the skin due to uroporphyrin I and coproporphyrin I accumulation. It also causes erythrocyte fragility leading to haemolytic anaemia. The other clinical features include hirsutism, red discolouration of teeth, finger-nails and urine and stunted growth. The outcome is poor, and the disfiguring nature of GD may partly explain the legend of the werewolf. No curative treatment was known until 1991, when the first case of BMT in GD was reported. The clinical and biological outcome after transplantation was encouraging, with an important regression of the symptoms of the disease, but the child died of CMV-infection 11 months after BMT. We report the second case of GD treated successfully by stem cell transplantation using umbilical cord blood from an HLA-identical brother in a 4-year-old girl suffering from severe GD. Our patient is very well 10 months after transplantation. We confirm that stem cell transplantation is curative for GD.

Porphyrias: animal models and prospects for cellular and gene therapy

The rapid progress in the development of molecular technology has resulted in the identification of most of the genes of the heme biosynthesis pathway. Important problems in the pathogenesis and treatment of porphyrias now seem likely to be solved by the possibility of creating animal models and by the transfer of normal genes or cDNAs to target cells. Animal models of porphyrias naturally occur for erythropoietic protoporphyria and congenital erythropoietic porphyria, and different murine models have been or are being created for erythropoietic and hepatic porphyrias. The PBGD knock-out mouse will be useful for the understanding of nervous system dysfunction in acute porphyrias. Murine models of erythropoietic porphyrias are being used for bone-marrow transplantation experiments to study the features of erythropoietic and hepatic abnormalities. Gene transfer experiments have been started in vitro to look at the feasibility of somatic gene therapy in erythropoietic porphyrias. In particular, we have documented sufficient gene transfer rate and metabolic correction in different CEP disease cells to indicate that this porphyria is a good candidate for treatment by gene therapy in hematopoietic stem cells. With the rapid advancement of methods that may allow more precise and/or efficient gene targeting, gene therapy will become a new therapeutic option for porphyrias.

Metabolic correction of congenital erythropoietic porphyria by retrovirus-mediated gene transfer into Epstein-Barr virus-transformed B-cell lines

Congenital erythropoietic porphyria (CEP) is an inherited metabolic disorder resulting from the accumulation of porphyrins because of defective uroporphyrinogen III synthase (UROIIIS). This autosomal recessive disorder is phenotypically heterogeneous with respect to the age of onset and the severity of the symptoms. Different exonic point mutations in the UROIIIS gene have been identified, providing phenotype-genotype correlations in this disease. Severe cases may be treated by bone marrow transplantation and are potential candidates for somatic gene therapy. Epstein-Barr virus-transformed B-cell lines from patients with CEP provide a model system for the disease. We have used retrovirus-mediated expression of UROIIIS to restore enzymatic activity in a B-cell line from a patient. We have also demonstrated the metabolic correction of the disease, ie, porphyrin accumulation into the deficient transduced cells was reduced to the normal level. These data show the potential of gene therapy for this disease.

Porphyria in childhood

Porphyria in childhood is an uncommon problem but the recognition of these disorders is vitally important for affected children. Of the cutaneous porphyrias, erythropoietic protoporphyria, congenital erythropoietic porphyria, hepatoerythropoietic porphyria, and the hereditary form of porphyria cutanea tarda (PCT) can present in infancy or childhood. This article focuses on the porphyrias that present in infants and children along with a brief discussion of pathogenesis, cutaneous histopathology, and genetics of these metabolic disorders.

Correction of the enzyme defect in cultured congenital erythropoietic porphyria disease cells by retrovirus-mediated gene transfer

Congenital erythropoietic porphyria (CEP) is a genetic disease characterized by an overproduction and accumulation of porphyrins in bone marrow. The enzyme defect concerns uroporphyrinogen III synthase (UROIIIS), the fourth enzyme of the heme biosynthetic pathway. It is the most severe porphyria and the treatment is largely symptomatic: gene therapy would represent a great therapeutic improvement. As a step toward the development of an effective gene therapy, we have constructed two retroviral vectors, LUSN and pMFG-US (with and without the selectable marker Neo), containing a full-length human cDNA for UROIIIS. Recombinant retroviruses were obtained by transfection of the LUSN or pMFG-US plasmid into the amphotropic packaging cell line psi CRIP. For each construct, three different producing clones were selected for their high titer (LUSN) or for their ability to express the message at a high level (pMFG-US). In vitro amplification of genomic DNA from target tissue demonstrated the presence of vector sequences. Murine fibroblasts infected in vitro expressed the human enzyme efficiently, as indicated by RNA and enzymatic studies. Retroviral-mediated gene transfer was then used to introduce the UROIIIS cDNA into human deficient cells. Enzyme activity was increased from 2% (deficient fibroblasts) to 121-274% of the normal value for the different clones. Transduced cells selected with G418 presented an 18-fold increase in enzyme activity compared to the normal cells. Furthermore, high gene transfer rate into peripheral blood progenitor cells (PBPB) was documented by in vitro amplification (PCR). These results demonstrate the potential usefulness of somatic gene therapy for the treatment of CEP.