Correction of congenital erythropoietic porphyria by bone marrow transplantation

Severe Perinatal Presentations of Günther's Disease: Series of 20 Cases and Perspectives

(1) Background: Congenital erythropoietic porphyria (CEP), named Günther's disease, is a rare recessive type of porphyria, resulting from deficient uroporphyrinogen III synthase (UROS), the fourth enzyme of heme biosynthesis. The phenotype ranges from extremely severe perinatal onset, with life-threatening hemolytic anaemia, to mild or moderate cutaneous involvement in late-onset forms. This work reviewed the perinatal CEP cases recorded in France in order to analyse their various presentations and evolution. (2) Methods: Clinical and biological data were retrospectively collected through medical and published records. (3) Results: Twenty CEP cases, who presented with severe manifestations during perinatal period, were classified according to the main course of the disease: antenatal features, acute neonatal distress and postnatal diagnosis. Antenatal symptoms (seven patients) were mainly hydrops fetalis, hepatosplenomegaly, anemia, and malformations. Six of them died prematurely. Five babies showed acute neonatal distress, associated with severe anemia, thrombocytopenia, hepatosplenomegaly, liver dysfunction, and marked photosensitivity leading to diagnosis. The only two neonates who survived underwent hematopoietic stem cell transplantation (HSCT). Common features in post-natal diagnosis (eight patients) included hemolytic anemia, splenomegaly, skin sensitivity, and discoloured teeth and urine. All patients underwent HSCT, with success for six of them, but with fatal complications in two patients. The frequency of the missense variant named C73R is striking in antenatal and neonatal presentations, with 9/12 and 7/8 independent alleles, respectively. (4) Conclusions: The most recent cases in this series are remarkable, as they had a less fatal outcome than expected. Regular transfusions from the intrauterine period and early access to HSCT are the main objectives.

Mutation-Specific Guide RNA for Compound Heterozygous Porphyria On-target Scarless Correction by CRISPR/Cas9 in Stem Cells

CRISPR/Cas9 is a promising technology for gene correction. However, the edition is often biallelic, and uncontrolled small insertions and deletions (indels) concomitant to precise correction are created. Mutation-specific guide RNAs were recently tested to correct dominant inherited diseases, sparing the wild-type allele. We tested an original approach to correct compound heterozygous recessive mutations. We compared editing efficiency and genotoxicity by biallelic guide RNA versus mutant allele-specific guide RNA in iPSCs derived from a congenital erythropoietic porphyria patient carrying compound heterozygous mutations resulting in UROS gene invalidation. We obtained UROS function rescue and metabolic correction with both guides with the potential of use for porphyria clinical intervention. However, unlike the biallelic one, the mutant allele-specific guide was free of on-target collateral damage. We recommend this design to avoid genotoxicity and to obtain on-target scarless gene correction for recessive disease with frequent cases of compound heterozygous mutations.

Bone Marrow Transplantation in Congenital Erythropoietic Porphyria: Sustained Efficacy but Unexpected Liver Dysfunction

Congenital erythropoietic porphyria (CEP) is a rare disease characterized by erosive photosensitivity and chronic hemolysis due to a defect of the enzyme uroporphyrinogen-III-synthase (UROS). To date, hematopoietic stem cell transplantation (HSCT) is the only curative therapy for the devastating early and severe form of the disease. We describe 6 patients with CEP treated with HSCT (3 of them twice after failure of a first graft) between 1994 and 2016 in our center, including 2 of the very first living patients treated more than 20 years ago. Four patients are doing well at 6 to 25 years post-HSCT, with near-normal biochemical parameters of porphyrin metabolism without the cutaneous or hematologic features of CEP. One patient died within the first year after HSCT from severe graft-versus-host disease (GVHD), and 1 child died of unexplained acute hepatic failure at 1 year after HSCT, despite full donor chimerism. Retrospectively, it appears that all but 1 child had increased transaminase activity with onset from the early postnatal period, which was significantly more marked in the child who died of liver failure. In contrast, liver function values progressively normalized after engraftment in all other children. Liver pathology before HSCT for 3 patients revealed varying degrees of portal, centrilobular, and perisinusoidal fibrosis; clarification of hepatocytes; and cytosolic porphyrin deposits. The liver porphyrin content in biopsy specimens was >60 times the normal values. Despite difficult engraftment, the long-term efficacy of HSCT in CEP appears to be favorable and reinforces its benefits for the severe form of CEP. Hepatic involvement requires careful evaluation before and after HSCT and further investigation into its pathophysiology and care.

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.

Inducing iron deficiency improves erythropoiesis and photosensitivity in congenital erythropoietic porphyria

Congenital erythropoietic porphyria (CEP) is an autosomal recessive disorder of heme synthesis characterized by reduced activity of uroporphyrinogen III synthase and the accumulation of nonphysiologic isomer I porphyrin metabolites, resulting in ineffective erythropoiesis and devastating skin photosensitivity. Management of the disease primarily consists of supportive measures. Increased activity of 5-aminolevulinate synthase 2 (ALAS2) has been shown to adversely modify the disease phenotype. Herein, we present a patient with CEP who demonstrated a remarkable improvement in disease manifestations in the setting of iron deficiency. Hypothesizing that iron restriction improved her symptoms by decreasing ALAS2 activity and subsequent porphyrin production, we treated the patient with off-label use of deferasirox to maintain iron deficiency, with successful results. We confirmed the physiology of her response with marrow culture studies.

Cutaneous porphyrias part II: treatment strategies

The porphyrias are diverse in pathophysiology, clinical presentation, severity, and prognosis, presenting a diagnostic and therapeutic challenge. Although not easily curable, the dermatological manifestations of these diseases, photosensitivity and associated cutaneous pathology, can be effectively prevented and managed. Sun avoidance is essential, and patient education regarding the irreversibility of photocutaneous damage is a necessary corollary. Beyond preventative measures, the care of fragile, vulnerable skin, and pain management, each of the porphyrias has a limited number of unique additional therapeutic options. Many of the treatments have been published only in small case series or anecdotal reports and do not have well-understood nor proven mechanisms of action. This article presents a comprehensive review of available therapeutic options and long-term management recommendations for the cutaneous porphyrias.

Successful treatment of congenital erythropoietic porphyria using matched unrelated hematopoietic stem cell transplantation

Congenital erythropoietic porphyria (CEP), or Günther's disease, is an inborn error of metabolism produced by a deficiency of uroporphyrinogen III synthase (UROS), the fourth enzyme of the heme biosynthesis pathway. This enzymatic defect induces the accumulation of isomer I porphyrins in erythrocytes, skin, and tissues, producing various clinical manifestations. Severe cases are characterized by extreme photosensitivity, causing scarring and mutilations, and by hemolytic anemia, reducing life expectancy. CEP is caused by mutations in the UROS gene, and one of the most severe forms of the disease is associated with a cysteine to arginine substitution at residue 73 of the protein (C73R). CEP has been successfully treated only by the transplantation of hematopoietic precursors. We report the case of a male infant with severe postdelivery symptoms diagnosed with CEP and found to be homozygous for the C73R mutation. He underwent successful allogeneic bone marrow transplantation from a matched unrelated donor at 7 months of age. The hemolytic anemia was corrected and the porphyrin overproduction was significantly reduced. The patient remained asymptomatic after 1 year. This new case confirms that patients with severe CEP can benefit from early postnatal hematopoietic stem cell transplantation.

Report of a novel Indian case of congenital erythropoietic porphyria and overview of therapeutic options

Congenital erythropoietic porphyria is a rare disorder of heme biosynthesis, resulting from decreased enzymatic activity of uroporphyrinogen III synthase. Clinical manifestations are heterogenous, of variable severity, and with occasional phenotypic-genotypic correlation. A 14-month-old boy developed fever, extensive dermatitis, and reddish colored urine. Anemia, erythrodontia, hepatosplenomegaly, and massive urinary elimination of predominantly type I porphyrins was suggestive of congenital erythropoietic porphyria. Although hemolysis remained mild and compensated, facial and digital mutilation developed indicative of moderate clinical phenotype. Mutational analysis revealed compound heterozygosity of mutant alleles, including a novel mutation (p.Pro190Leu). The child received supportive management and underwent facial reconstruction successfully.

A management algorithm for congenital erythropoietic porphyria derived from a study of 29 cases

BACKGROUND

Congenital erythropoietic porphyria (CEP) is an autosomal recessive photomutilating porphyria with onset usually in childhood, where haematological complications determine prognosis. Due to its extreme rarity and clinical heterogeneity, management decisions in CEP are often difficult.

OBJECTIVES

To develop a management algorithm for patients with CEP based on data from carefully characterized historical cases.

METHODS

A single investigator collated data related to treatments and their outcomes in 29 patients with CEP from the U.K., France, Germany and Switzerland.

RESULTS

Six children were treated with bone marrow transplantation (BMT); five have remained symptomatically cured up to 11.5 years post-transplantation. Treatments such as oral charcoal, splenectomy and chronic hypertransfusion were either of no benefit or were associated with complications and negative impact on health-related quality of life. Lack of consistent genotype-phenotype correlation meant that this could not be used to predict disease prognosis. The main poor prognostic factors were early age of disease onset and severity of haematological manifestations.

CONCLUSIONS

A management algorithm is proposed where every patient, irrespective of disease severity at presentation, should receive a comprehensive, multidisciplinary clinical assessment and should then be reviewed at intervals based on their predicted prognosis, and the rate of onset of complications. A BMT should be considered in those with progressive, symptomatic haemolytic anaemia and/or thrombocytopenia. Uroporphyrinogen III synthase genotypes associated with poor prognosis would additionally justify consideration for a BMT. Rigorous photoprotection of the skin and eyes from visible light is essential in all patients.

Congenital erythropoietic porphyria: characterization of murine models of the severe common (C73R/C73R) and later-onset genotypes

Congenital erythropoietic porphyria (CEP) is an autosomal recessive disorder due to the deficient activity of uroporphyrinogen III synthase (UROS). Knock-in mouse models were generated for the common, hematologically severe human genotype, C73R/C73R, and milder genotypes (C73R/V99L and V99L/V99L). The specific activities of the UROS enzyme in the livers and erythrocytes of these mice averaged approximately 1.2%, 11% and 19% of normal, respectively. C73R/C73R mice that survived fetal life to weaning age (~12%) had a severe microcytic hypochromic anemia (hemoglobin 7.9 g/dL, mean cellular volume 26.6 fL, mean cellular hemoglobin content 27.4 g/dL, red cell distribution width 37.7%, reticulocytes 19%) and massively accumulated isomer I porphyrins (95, 183 and 44 μmol/L in erythrocytes, spleen and liver, respectively), but a nearly normal lifespan. In adult C73R/C73R mice, spleen and liver weights were 8.2- and 1.5-fold increased, respectively. C73R/V99L mice were mildly anemic (hemoglobin was 14.0 g/dL and mean cellular hemoglobin was 13.3), with minimally accumulated porphyrins (0.10, 5.54 and 0.58 μmol/L in erythrocytes, spleen and liver, respectively), whereas adult V99L/V99L mice were normal. Of note, even the mildest genotype, V99L/V99L, exhibited porphyria in utero, which disappeared by 2 months of age. These severe and mild mouse models inform therapeutic interventions and permit further investigation of the porphyrin-induced hematopathology, which leads to photo-induced cutaneous lesions. Of significance for therapeutic intervention, these mouse models suggest that only 11% of wild-type activity might be needed to reverse the pathology in CEP patients.

Effective gene therapy of mice with congenital erythropoietic porphyria is facilitated by a survival advantage of corrected erythroid cells

Achieving long-term expression of a therapeutic gene in a given hematopoietic lineage remains an important goal of gene therapy. Congenital erythropoietic porphyria (CEP) is a severe autosomal-recessive disorder characterized by a deficiency in uroporphyrinogen III synthase (UROS), the fourth enzyme of the heme biosynthetic pathway. We used a recently obtained murine model to check the feasibility of gene therapy in this disease. Lentivirus-mediated transfer of the human UROS cDNA into hematopoietic stem cells (HSCs) from Uros(mut248) mice resulted in a complete and long-term enzymatic, metabolic, and phenotypic correction of the disease, favored by a survival advantage of corrected red blood cells. These results demonstrate that the cure of this mouse model of CEP at a moderate transduction level supports the proof of concept of a gene therapy in this disease by transplantation of genetically modified hematopoietic stem cells.

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.

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.

Childhood porphyrias

Childhood porphyrias are an uncommon group of metabolic disorders that result from inherited deficiencies of enzymes involved in the heme biosynthetic pathway. Although childhood porphyrias have been reported globally, their exact incidence is unknown. The inheritance patterns of these disorders are complex. Phenotypic variability is common among individual disease states and results partly from the presence of genetic heterogeneity. Childhood porphyrias typically present with photosensitivity and unique skin lesions. Therapy is limited and consists mostly of symptomatic and preventive measures. Although the disease course is variable, mortality from these disorders is rare.

Allogeneic bone marrow transplantation in a child with hemoglobinopathy olmsted

The authors describe the first successful bone marrow transplant for the treatment of hemoglobinopathy Olmsted in a boy who presented with severe transfusion-dependent hemolytic anemia and jaundice at age 4 months. He received bone marrow from an HLA-identical sibling with normal hemoglobin electrophoresis after conditioning with busulfan, cyclophosphamide, and antithymocyte globulin when he was 18 months old. The posttransplant course was uneventful. Two years after transplantation the patient has a normal hemoglobin level without evidence of hemolysis. DNA analysis shows 100% chimerism of donor cell origin, confirming full engraftment with normal hematopoietic cells.

Bone marrow transplantation for nonmalignant diseases

Bone marrow transplantation (BMT) has emerged as a major therapeutic option for a number of nonmalignant disorders affecting the bone marrow and leading to clinical manifestations most likely affecting distant organs. Disorders such as autoimmune diseases, metabolic disorders, hemoglobinopathies, immunodeficiencies, and others have been the target of high-dose therapy and autologous or allogeneic bone marrow, stem cell, or cord blood transplantation. Successful results have been reported in a large number of these disorders. In most instances the goal of transplantation is to provide sufficient degree of marrow engraftment to allow long-term amelioration of disease phenotype. For many of these disorders, early diagnosis is crucial in achieving the desired results as transplantation becomes difficult when significant end-organ damage sets in. Major unsolved problems, including toxicity of conditioning regimens, graft-versus-host disease, and donor availability, need to be addressed. We attempt to provide a comprehensive review of BMT and discuss unique features of this modality for treatment of nonmalignant disorders.

Gene therapy of a mouse model of protoporphyria with a self-inactivating erythroid-specific lentiviral vector without preselection

Successful treatment of blood disorders by gene therapy has several complications, one of which is the frequent lack of selective advantage of genetically corrected cells. Erythropoietic protoporphyria (EPP), caused by a ferrochelatase deficiency, is a good model of hematological genetic disorders with a lack of spontaneous in vivo selection. This disease is characterized by accumulation of protoporphyrin in red blood cells, bone marrow, and other organs, resulting in severe skin photosensitivity. Here we develop a self-inactivating lentiviral vector containing human ferrochelatase cDNA driven by the human ankyrin-1/beta-globin HS-40 chimeric erythroid promoter/enhancer. We collected bone marrow cells from EPP male donor mice for lentiviral transduction and injected them into lethally irradiated female EPP recipient mice. We observed a high transduction efficiency of hematopoietic stem cells resulting in effective gene therapy of primary and secondary recipient EPP mice without any selectable system. Skin photosensitivity was corrected for all secondary engrafted mice and was associated with specific ferrochelatase expression in the erythroid lineage. An erythroid-specific expression was sufficient to reverse most of the clinical and biological manifestations of the disease. This improvement in the efficiency of gene transfer with lentiviruses may contribute to the development of successful clinical protocols for erythropoietic diseases.

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.

The heme biosynthesis pathway and clinical manifestations of abnormal function

Biosynthesis of heme is important for both prokaryotes and eukaryotes. The enzymes for this multistep process are distributed between the cytosol and mitochondria in eukaryotes. In humans there are inherited and acquired disorders characterized by over synthesis of one or more enzymes or absence of an enzyme. This overview discusses each enzyme in the heme biosynthesis pathway.

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.

Congenital porphyria with necrotizing scleritis in a 9-year-old child

Porphyria is a rare metabolic disorder that is characterized by the accumulation of photosensitive, toxic intermediates of the heme metabolic pathway in various organs of the body including the skin, eye and neural tissue. Porphyria as a potential cause for bilateral necrotizing scleritis in children is very infrequently emphasized in literature, probably due to the relatively rare occurrence and lack of well-documented cases. A case of a 9-year-old child with congenital porphyria who had developed necrotizing scleral ulceration in both eyes in addition to severe cutaneous hypersensitivity and facial disfigurement is herein presented.

Congenital erythropoietic porphyria affecting two brothers

We report two brothers, aged 5 and 2 years, with typical features of congenital erythropoietic porphyria. The elder did not receive medical attention until the age of 2 years, even though his urine had been red almost from birth, and despite severe scarring of the hands and face. The younger brother suffered haemolysis at birth. The uroporphyrinogen III cosynthase (URO IIIS) enzyme activity of red blood cells was 2% and 1.2% in the brothers, and genetic studies showed two different mutations of the URO IIIS gene, C73R and P248Q. The latter is a recently described mutation.

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 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 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: 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.

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.

[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.