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

The Hepatic Porphyrias: Revealing the Complexities of a Rare Disease

The porphyrias are a group of metabolic disorders that are caused by defects in heme biosynthesis pathway enzymes. The result is accumulation of heme precursors, which can cause neurovisceral and/or cutaneous photosensitivity. Liver is commonly either a source or target of excess porphyrins, and porphyria-associated hepatic dysfunction ranges from minor abnormalities to liver failure. In this review, the first of a three-part series, we describe the defects commonly found in each of the eight enzymes involved in heme biosynthesis. We also discuss the pathophysiology of the hepatic porphyrias in detail, covering epidemiology, histopathology, diagnosis, and complications. Cellular consequences of porphyrin accumulation are discussed, with an emphasis on oxidative stress, protein aggregation, hepatocellular cancer, and endothelial dysfunction. Finally, we review current therapies to treat and manage symptoms of hepatic porphyria.

Congenital erythropoietic porphyria with erythrodontia: A case report

BACKGROUND

The causes for intrinsic tooth discoloration can be separated into two categories as systemic and local. Systemic causes are either genetic or drug-induced effects. The development of dentition can also be affected by a number of systemic factors and metabolic diseases such as porphyria. Congenital erythropoietic porphyria (CEP), also known as Gunther's disease, is a metabolic disease caused by a transformation in the gene that codifies uroporphyrinogen-3 synthesis, leading to porphyrin aggregation in urine, skin, bone, and dentin.

CASE REPORT

A 21-month-old girl with erythrodontia was referred to Paediatric Dentistry Department in September 2017. A physical examination revealed blisters on her face, nose, hands, and feet. Laboratory findings showed highly elevated urine total uroporphyrin and total coproporphyrin I and III levels. Next-generation sequencing multigene panel testing for porphyria demonstrated a homozygous c.10C>T (p.L4F) mutation in the UROS gene. For curative therapy, the patient was admitted to the allogeneic bone marrow transplantation program.

CONCLUSION

Congenital erythropoietic porphyria most commonly presents in the first few years of life. Manifestations can include reddish-colored urine, skin blistering, scarring, and erythrodontia. A timely diagnosis can prevent undesirable skin findings of the disease and death due to hematological involvement before a curative allogeneic bone marrow transplantation is performed.

[Congenital erythropoietic porphyria : An update]

BACKGROUND

Congenital erythropoetic porphria is a very rare type of autosomal recessive nonacute porphyria. Homozygous or compound heterozygous mutations in the uroporphyrinogen III consynthase gene cause a marked enzymatic deficiency of uroporphyrinogen III consynthase, the fourth enzyme along the heme biosynthetic pathway.

CLINICAL PRESENTATION

Clinically, affected patients are characterized by a moderate to severe photosensitivity. Starting early in infancy, they develop blisters, erosions, and exulcerations in sun-exposed areas of the body, often resulting in scar formation and mutilation. Besides the cutaneous changes, hemolytic anemia, transfusion-dependent pancytopenia, hepatosplenomegaly and liver cirrhosis can occur. Due to increased susceptibility for infections and because of the hematological and hepatic complications, affected individuals have a decreased life expectancy, rarely exceeding 40 years of age.

TREATMENT

Currently, no causal treatment is available for the disorder. Therefore, the most important therapeutic modality is strict avoidance of sunlight, preferably by inversion of the day-night rhythm, or at least consequent photoprotection with adequate clothing. In severe cases, bone marrow or stem cell transplantation should be considered.

Feline congenital erythropoietic porphyria: two homozygous UROS missense mutations cause the enzyme deficiency and porphyrin accumulation

The first feline model of human congenital erythropoietic porphyria (CEP) due to deficient uroporphyrinogen III synthase (URO-synthase) activity was identified by its characteristic clinical phenotype, and confirmed by biochemical and molecular genetic studies. The proband, an adult domestic shorthair cat, had dark-red urine and brownish discolored teeth with red fluorescence under ultraviolet light. Biochemical studies demonstrated markedly increased uroporphyrinogen I in urine and plasma (2,650- and 10,700-fold greater than wild type, respectively), whereas urinary 5-aminolevulinic acid and porphobilinogen were lower than normal. Erythrocytic URO-synthase activity was <1% of mean wild-type activity, confirming the diagnosis and distinguishing it from feline phenocopies having acute intermittent porphyria. Sequencing of the affected cat's UROS gene revealed two missense mutations, c.140C>T (p.S47F) in exon 3 and c.331G>A (p.G111S) in exon 6, both of which were homozygous, presumably owing to parental consanguinity. Neither was present in 100 normal cat alleles. Prokaryotic expression and thermostability studies of the purified monomeric wild-type, p.S47F, p.G111S, and p.S47F/G111S enzymes showed that the p.S47F enzyme had 100% of wild-type specific activity but ~50% decreased thermostability, whereas the p.G111S and p.S47F/G111S enzymes had about 60% and 20% of wild-type specific activity, respectively, and both were markedly thermolabile. Molecular modeling results indicated that the less active/less stable p.G111S enzyme was further functionally impaired by a structural interaction induced by the presence of the S47F substitution. Thus, the synergistic interaction of two rare amino acid substitutions in the URO-synthase polypeptide caused the feline model of human CEP.

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.

Uroporphyrinogen III synthase knock-in mice have the human congenital erythropoietic porphyria phenotype, including the characteristic light-induced cutaneous lesions

Congenital erythropoietic porphyria (CEP), an autosomal recessive inborn error, results from the deficient but not absent activity of uroporphyrinogen III synthase (URO-synthase), the fourth enzyme in the heme biosynthetic pathway. The major clinical manifestations include severe anemia, erythrodontia, and disfiguring cutaneous involvement due to the accumulation of phototoxic porphyrin I isomers. Murine models of CEP could facilitate studies of disease pathogenesis and the evaluation of therapeutic endeavors. However, URO-synthase null mice were early embryonic lethals. Therefore, knock-in mice were generated with three missense mutations, C73R, V99A, and V99L, which had in vitro-expressed activities of 0.24%, 5.9%, and 14.8% of expressed wild-type activity, respectively. Homozygous mice for all three mutations were fetal lethals, except for mice homozygous for a spontaneous recombinant allele, V99A(T)/V99A(T), a head-to-tail concatemer of three V99A targeting constructs. Although V99A(T)/V99A(T) and C73R/V99A(T) mice had approximately 2% hepatic URO-synthase activity and normal hepatic microsomal heme and hemoprotein levels, they had 20% and 13% of wild-type activity in erythrocytes, respectively, which indicates that sufficient erythroid URO-synthase was present for fetal development and survival. Both murine genotypes showed marked porphyrin I isomer accumulation in erythrocytes, bone, tissues, and excreta and had fluorescent erythrodontia, hemolytic anemia with reticulocytosis and extramedullary erythropoiesis, and, notably, the characteristic light-induced cutaneous involvement. These mice provide insight into why CEP is an erythroid porphyria, and they should facilitate studies of the disease pathogenesis and therapeutic endeavors for CEP.

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.

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.

Congenital erythropoietic porphyria: identification and expression of eight novel mutations in the uroporphyrinogen III synthase gene

Mutations in the uroporphyrinogen III synthase (URO-synthase) gene cause congenital erythropoietic porphyria (CEP), an autosomal recessive inborn error of haem biosynthesis. Molecular analysis of the URO-synthase gene in seven unrelated CEP patients revealed eight novel mutations. These included four missense mutations (A69T, E81D, G188W and I219S), a deletion (21delG), two insertions (398insG and 672ins28) and one complex mutation (627del6ins39), as well as three previously reported mutations, C73R, T228M, and -86C-->A. When the four novel missense mutations were expressed in Escherichia coli, only E81D expressed significant enzymatic activity (30% of expressed wild-type activity), which was thermolabile. In addition, reverse transcription polymerase chain reaction studies demonstrated that E81D, which altered the penultimate nucleotide in exon 4, impaired splicing and caused about 85% exon 4 skipping. The identification and expression of these mutations provided genotype-phenotype correlations and further evidence of the molecular heterogeneity underlying this erythropoietic porphyria.

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.

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.