New insights into the pathogenesis of erythropoietic protoporphyria and their impact on patient care

Living-Donor Liver Transplantation for Erythropoietic Protoporphyria: A Case Report and Literature Review

Erythropoietic protoporphyria (EPP) is a very rare disease with an estimated prevalence of 1 in 200,000 individuals. Decreased ferrochelatase activity causes the accumulation of protoporphyrin in the body, and light exposure results in the generation of active oxygen, causing photosensitivity. Liver damage has the greatest influence on the prognosis, and liver transplantation is the only treatment option for patients with decompensated liver cirrhosis. We report a case of living-donor liver transplantation for decompensated liver cirrhosis associated with EPP. The patient was a 52-year-old male who led a normal life except for mild photosensitivity. When the patient was 37-year-old, hepatic dysfunction was noticed. At 48-year-old, high erythrocyte protoporphyrin levels, skin biopsy, and genetic tests resulted in a diagnosis of EPP. The patient underwent living- donor liver transplantation because of decompensated liver cirrhosis. In the operating room and intensive care unit, a special light-shielding film was applied to all light sources to block light with harmful wavelengths during treatment. Due to the need for special measures, a lecture on patients with EPP was given before surgery to deepen understanding among all medical professionals involved in the treatment. As a result, no adverse events occurred during the perioperative period, and the patient was discharged on the 46th post-operative day. Currently, the transplanted liver is functioning extremely well, and the patient is alive 3 years post-transplant. Herein, we describe a case of living donor liver transplantation for EPP with a brief literature review.

Definitive Confirmation of Erythropoietic Protoporphyria via Re-biopsy Three Years After Initial Liver Biopsy at Age 15

Erythropoietic protoporphyria (EPP) is a rare inherited disorder of porphyrin metabolism that can cause liver damage and cholestatic hepatocellular failure. We report a case of EPP in a teenaged male who underwent liver biopsy for investigation of liver dysfunction of unknown cause. The diagnosis was not made until a re-biopsy approximately three years later, when the patient presented with recurrent skin lesions and elevated blood and urinary protoporphyrin levels. The liver biopsies contained brownish deposits that exhibited birefringence under polarized light and porphyrin fluorescence under fluorescence spectroscopy. EPP should be considered in young patients with unexplained liver dysfunction, skin symptoms, and seasonal changes in symptoms. Fluorescence spectroscopy of liver biopsy tissue can be a useful tool in the diagnosis of EPP.

Single-incision laparoscopic partial cecectomy for appendiceal mucocele in a patient with porphyria photosensitivity

Erythropoietic protoporphyria (EPP) is a rare hereditary subtype of cutaneous porphyria characterized by photosensitivity. Increased exposure to light irradiation may precipitate acute liver failure, and surgical light-induced intestinal burns and perforations are known to occur. We report a case of EPP in a patient who underwent laparoscopic partial cecectomy for appendiceal mucocele. A 55-year-old man with EPP was presented for treatment of appendiceal mucocele. A light test using two types of laparoscopes (Companies O and S) was performed preoperatively. Light from the laparoscope manufactured by Company O caused photosensitivity; this effect was not observed with light from the laparoscope manufactured by Company S. Therefore, we performed laparoscopic partial cecectomy through a single umbilical incision using the laparoscope from Company S. Except for the incision site, the patient's skin was completely covered using surgical drapes. No intra- or postoperative complications were observed. Histopathological examination of the resected specimen revealed a low-grade appendiceal mucinous neoplasm.

Increased phototoxic burn tolerance time and quality of life in patients with erythropoietic protoporphyria treated with afamelanotide - a three years observational study

BACKGROUND

Erythropoietic protoporphyria (EPP) is an ultra-rare genetic disorder (prevalence 1:150`000) characterized by instant painful phototoxic burn reactions in skin exposed to visible light. Afamelanotide is the first clinically tested therapy effectively increasing the time EPP patients can spend in direct sunlight without developing symptoms and reducing the number and severity of phototoxic reactions.

OBJECTIVES

We report our data on real-world effectiveness of afamelanotide treatment in EPP and its phototoxic burn protection factor (PBPF).

METHODS

We analysed clinical data collected between 2016 and 2018 in the Swiss EPP cohort (n = 39) on maximum phototoxic burn tolerance time (PBTT), i.e., maximum time spent in sunlight without phototoxic reaction, severity of phototoxic reactions as assessed by an 11-point Likert-type visual analogue scale (VAS), with 0 being no pain and 10 being the worst possible pain, and Quality of Life (QoL), as assessed with an EPP-specific instrument.

RESULTS

Before treatment, the PBTT was median 10 min (IQR 5-20). Under treatment, PBTT increased to median 180 min (IQR 120-240). Individual PBPF increased 1.8- to 180-fold (full range, median 15). The pain severity of the worst phototoxic reaction before treatment was median 10 and under treatment median 6 (IQR 3-7). QoL at the end of the observation period in 2018 (with all the assessed patients under treatment) was 81.4% (IQR 69.4-93.4, n = 34). A 97.4% treatment adherence rate was observed.

CONCLUSION

Treatment of EPP patients with afamelanotide is highly effective under real-world conditions. We suggest PBTT as a clinical meaningful endpoint in further clinical trials.

Successful Liver Transplantation for Liver Failure With Erythropoietic Protoporphyria by Covering the Operating Theater Lights With Polyimide Film: A Case Report

BACKGROUND

Erythropoietic protoporphyria is a rare disease of heme biosynthesis resulting in excessive accumulation of protoporphyrin in various organs. The most typical symptom is photosensitivity caused by activated protoporphyrins (wavelength ~400 nm). Accumulated protoporphyrin in the liver also causes liver failure, and liver transplantation is the only life-saving treatment. Phototoxic injury to abdominal organs has been reported during liver transplantation. Thus, to avoid phototoxic injury during liver transplantation, it has previously been conducted with only shadowless lights and ceiling lights off in the operating theater. Here, we report a case of a safe and successful liver transplantation in a patient with erythropoietic protoporphyria where the operating theater lights were covered with polyimide film.

CASE PRESENTATION

A 50-year-old man presented with hepatic failure owing to erythropoietic protoporphyria. Before liver transplantation, the shadowless lights and ceiling lights in the operating theater were covered entirely with polyimide film. This filter completely blocked the harmful wavelength of light (400-470 nm). Orthotopic liver transplantation was safely and successfully performed with adequate illumination and patient monitoring. The patient followed a normal postoperative course without phototoxic injuries or protoporphyrin re-accumulation.

CONCLUSION

Covering not only shadowless lights but also all ceiling lights in the operating theater with the polyimide film allowed safe surgery, safe anesthesia, and safe monitoring of the patient who underwent liver transplantation for severe liver failure owing to erythropoietic protoporphyria.

Patient empowerment and access to medicines: Insights from a scientist-patient suffering from erythropoietic protoporphyria

Patient representation during the evaluation of medicines by key decision makers such as regulatory agencies, Health Technology Assessment bodies, and healthcare payers is increasingly considered to add value to the appraisals and empowers patients, which means that they gain a more powerful voice over decisions and actions affecting their own health. As I myself suffer from the ultra-rare condition erythropoietic protoporphyria (EPP), I have participated as a patient expert in several discussions on access to afamelanotide, which currently is the only treatment for EPP and was approved in the European Union (EU) in 2014. As a molecular biologist with a PhD in EPP research, I consider myself having the necessary requirements to meaningfully contribute to such assessments. In this article, I share my personal experiences with regard to the discussions on access in Germany and England at the respective national competent authorities, the Federal Joint Committee, and the National Institute for Health and Care Excellence, respectively. In addition, I discuss the insights of the International Porphyria Patient Network, a group of highly empowered EPP patients effectively supporting national patient communities in their efforts to enable access to the afamelanotide treatment in their countries.

The incidence of inherited porphyrias in Europe

Retrospective estimates of the prevalence of porphyrias have been reported but there has been no large scale prospective study of their incidence. The European Porphyria Network collected information prospectively over a 3 year period about the number of newly diagnosed symptomatic patients with an inherited porphyria (335 patients from 11 countries). Prevalence was calculated from the incidence and mean disease duration. The incidence of hepato-cellular carcinoma (HCC) in acute hepatic porphyria and the prevalence of patients with recurrent acute attacks of porphyria were also investigated. The incidence of symptomatic acute intermittent porphyria (AIP) was similar in all countries (0.13 per million per year; 95 % CI: 0.10 - 0.14) except Sweden (0.51; 95 % CI: 0.28-0.86). The incidence ratio for symptomatic AIP: variegate porphyria: hereditary coproporphyria was 1.00:0.62: 0.15. The prevalence of AIP (5.4 per million; 95 % CI: 4.5-6.3) was about half that previously reported. The prevalence of erythropoietic protoporphyria (EPP) was less uniform between countries and, in some countries, exceeded previous estimates. Fourteen new cases of HCC (11 from Sweden) were reported in patients with acute porphyria. Sixty seven patients (3 VP; 64 AIP: 53 females, 11 males) with recurrent attacks of acute porphyria were identified. The estimated percentage of patients with AIP that will develop recurrent acute attacks was 3-5 %. In conclusion, the prevalence of symptomatic acute porphyria may be decreasing, possibly due to improved management, whereas the prevalence of EPP may be increasing due to improved diagnosis and its greater recognition as a cause of photosensitivity.

Protoporphyrin retention in hepatocytes and Kupffer cells prevents sclerosing cholangitis in erythropoietic protoporphyria mouse model

BACKGROUND & AIMS

Chronic, progressive hepatobiliary disease is the most severe complication of erythropoietic protoporphyria (EPP) and can require liver transplantation, although the mechanisms that lead to liver failure are unknown. We characterized protoporphyrin-IX (PPIX)-linked hepatobiliary disease in BALB/c and C57BL/6 (Fechm1Pas) mice with mutations in ferrochelatase as models for EPP.

METHODS

Fechm1Pas and wild-type (control) mice were studied at 12-14 weeks of age. PPIX was quantified; its distribution in the liver, serum levels of lipoprotein-X, liver histology, contents of bile salt and cholesterol phospholipids, and expression of genes were compared in mice of the BALB/c and C57BL/6 backgrounds. The in vitro binding affinity of PPIX for bile components was determined.

RESULTS

Compared with mice of the C57BL/6 background, BALB/c Fechm1Pas mice had a more severe pattern of cholestasis, fibrosis with portoportal bridging, bile acid regurgitation, sclerosing cholangitis, and hepatolithiasis. In C57BL/6 Fechm1Pas mice, PPIX was sequestrated mainly in the cytosol of hepatocytes and Kupffer cells, whereas, in BALB/c Fechm1Pas mice, PPIX was localized within enlarged bile canaliculi. Livers of C57BL/6 Fechm1Pas mice were protected through a combination of lower efflux of PPIX and reduced synthesis and export of bile acid.

CONCLUSIONS

PPIX binds to bile components and disrupts the physiologic equilibrium of phospholipids, bile acids, and cholesterol in bile. This process might be involved in pathogenesis of sclerosing cholangitis from EPP; a better understanding might improve diagnosis and development of reagents to treat or prevent liver failure in patients with EPP.

Porphyrias at a glance: diagnosis and treatment

Porphyrias are a group of eight rare inherited metabolic disorders of heme biosynthesis pathway. Porphyrias are still underdiagnosed, although examinations of urine and plasma are first-line tests for detecting excess of porphyrins or heme precursors in suspected patients. Diagnosis, particularly for the acute forms, is essential to avoid precipitating factors and the use of triggering drugs. Mutation screening of family members is recommended to identify presymptomatic carriers and to prevent acute attacks. The therapeutic approach should be appropriate regarding specific forms of porphyria and treatment should be started promptly.

Delayed immune recovery following sequential orthotopic liver transplantation and haploidentical stem cell transplantation in erythropoietic protoporphyria

A nine-yr-old boy with EPP suffered from severe skin burns and liver failure caused by progressive cholestasis and fibrosis. OLT was performed without major complications. Four months following liver transplantation he underwent parental haploidentical HSCT. The myeloablative conditioning regimen was relatively well tolerated and hematological engraftment was rapid (on day 10). Protoporphyrin concentrations returned to normal following HSCT. However, immune recovery was significantly delayed. Varicella zoster virus reactivation resulted in impaired vision, prolonged hospitalization and eventually in multiorgan failure and death. Sequential liver and haploidentical HSCT proved feasible though a high risk procedure in this EPP patient. The management of post-IST after these combined transplantations remains a challenge and needs to be further established.

Porphyrias

Hereditary porphyrias are a group of eight metabolic disorders of the haem biosynthesis pathway that are characterised by acute neurovisceral symptoms, skin lesions, or both. Every porphyria is caused by abnormal function of a separate enzymatic step, resulting in a specific accumulation of haem precursors. Seven porphyrias are the result of a partial enzyme deficiency, and a gain of function mechanism has been characterised in a new porphyria. Acute porphyrias present with acute attacks, typically consisting of severe abdominal pain, nausea, constipation, confusion, and seizure, and can be life-threatening. Cutaneous porphyrias present with either acute painful photosensitivity or skin fragility and blisters. Rare recessive porphyrias usually manifest in early childhood with either severe cutaneous photosensitivity and chronic haemolysis or chronic neurological symptoms with or without photosensitivity. Porphyrias are still underdiagnosed, but when they are suspected, and dependent on clinical presentation, simple first-line tests can be used to establish the diagnosis in all symptomatic patients. Diagnosis is essential to enable specific treatments to be started as soon as possible. Screening of families to identify presymptomatic carriers is crucial to decrease risk of overt disease of acute porphyrias through counselling about avoidance of potential precipitants.

Post-transcriptional regulation of the expression of ferrochelatase by its variant mRNA

Ferrochelatase (FECH) catalyses the insertion of ferrous ions into protoporphyrin IX to produce haem at the haem-biosynthetic pathway. The present study characterized a variant mRNA of mouse FECH, which was generated by skipping exon II (FECH-v). FECH-v mRNA was expressed in various tissues, including the liver and kidney, of mice. The mRNA was also expressed in mouse and human non-erythroid and erythroid cells to a different extent but could not be translated into functional FECH. The ratio of FECH-v/FECH increased in hemin-treated Balb/3T3 cells, while it decreased after treatment with succinylacetone, an inhibitor of haem biosynthesis, strongly suggesting that FECH expression was decreased by increasing the level of intracellular haem. These results demonstrated the haem-dependent negative feedback regulation of the expression of FECH at a post-transcriptional level.

Liver transplantation for erythropoietic protoporphyria with hepatic failure: a case report

Erythropoietic protoporphyria (EPP) is a disorder of heme synthesis in which deficient ferrochelatase activity leads to excessive production and biliary excretion of protoporphyrin. The main clinical features--photosensitivity and hepatobiliary disease that may progress to liver failure--are caused by the toxicity of protoporphyrin. Orthotopic liver transplantation is an effective treatment of liver failure caused by EPP. In this report we have described an EPP Chinese man with end-stage liver disease. He was successfully transplanted. A 3-year follow-up study of protoporphyrin levels, liver tests, and liver biopsies showed no EPP recurrence after liver transplantation.

Erythropoietic protoporphyria without skin symptoms-you do not always see what they feel

Erythropoietic protoporphyria (EPP) is an inherited disorder of the porphyrin metabolism that often remains undiagnosed in children. We report on a 4-year-old girl who had been suffering for 1 year from recurrent painful crises affecting her hands, feet, and nose following sun exposure. Objective skin lesions were absent until the age of 6. Porphyrin analysis revealed elevated free erythrocyte protoporphyrin (FEP) levels confirming the diagnosis of EPP. This illustrates that skin lesions might be completely absent in children affected with EPP, a fact that has only been reported once previously. Because EPP can manifest with few and unspecific cutaneous symptoms or no skin lesions at all, like in this patient, the diagnosis of EPP might be delayed or missed. EPP should be excluded in all photosensitive children, especially when discomfort is disproportionate to the extent of the cutaneous lesions. The clinic, pathophysiology, diagnosis, complications, and therapy of EPP are discussed.

Sequential liver and bone marrow transplantation for treatment of erythropoietic protoporphyria

Erythropoietic protoporphyria is a disorder of heme synthesis in which deficient ferrochelatase activity leads to excess production and biliary excretion of protoporphyrin. The main clinical features, photosensitivity and hepatobiliary disease that may progress to liver failure, are caused by the toxicity of protoporphyrin. Liver transplantation has been used to treat liver failure in erythropoietic protoporphyria, but excess production of protoporphyrin by the bone marrow continues causing recurrence of liver disease in the majority of patients. This is the first report of successful sequential liver and bone marrow transplantation in a patient with liver failure as a result of erythropoietic protoporphyria. This combination corrected the severe phenotype, resolving the severe photosensitivity and halting erythropoietic protoporphyria associated liver graft injury. Splenectomy seemed to facilitate the successful bone marrow transplant.

Increased plasma transferrin, altered body iron distribution, and microcytic hypochromic anemia in ferrochelatase-deficient mice

Patients with deficiency in ferrochelatase (FECH), the last enzyme of the heme biosynthetic pathway, experience a painful type of skin photosensitivity called erythropoietic protoporphyria (EPP), which is caused by the excessive production of protoporphyrin IX (PPIX) by erythrocytes. Controversial results have been reported regarding hematologic status and iron status of patients with EPP. We thoroughly explored these parameters in Fechm1Pas mutant mice of 3 different genetic backgrounds. FECH deficiency induced microcytic hypochromic anemia without ringed sideroblasts, little or no hemolysis, and no erythroid hyperplasia. Serum iron, ferritin, hepcidin mRNA, and Dcytb levels were normal. The homozygous Fechm1Pas mutant involved no tissue iron deficiency but showed a clear-cut redistribution of iron stores from peripheral tissues to the spleen, with a concomitant 2- to 3-fold increase in transferrin expression at the mRNA and the protein levels. Erythrocyte PPIX levels strongly correlated with serum transferrin levels. At all stages of differentiation in our study, transferrin receptor expression in bone marrow erythroid cells in Fechm1Pas was normal in mutant mice but not in patients with iron-deficiency anemia. Based on these observations, we suggest that oral iron therapy is not the therapy of choice for patients with EPP and that the PPIX–liver transferrin pathway plays a role in the orchestration of iron distribution between peripheral iron stores, the spleen, and the bone marrow.

Contribution of a common single-nucleotide polymorphism to the genetic predisposition for erythropoietic protoporphyria

Erythropoietic protoporphyria (EPP) is an inherited disorder of heme biosynthesis that results from a partial deficiency of ferrochelatase (FECH). Recently, we have shown that the inheritance of the common hypomorphic IVS3-48C allele trans to a deleterious mutation reduces FECH activity to below a critical threshold and accounts for the photosensitivity seen in patients. Rare cases of autosomal recessive inheritance have been reported. We studied a cohort of 173 white French EPP families and a group of 360 unrelated healthy subjects from four ethnic groups. The prevalences of the recessive and dominant autosomal forms of EPP are 4% (95% confidence interval 1-8) and 95% (95% confidence interval 91-99), respectively. In 97.9% of dominant cases, an IVS3-48C allele is co-inherited with the deleterious mutation. The frequency of the IVS3-48C allele differs widely in the Japanese (43%), southeast Asian (31%), white French (11%), North African (2.7%), and black West African (<1%) populations. These differences can be related to the prevalence of EPP in these populations and could account for the absence of EPP in black subjects. The phylogenic origin of the IVS3-48C haplotypes strongly suggests that the IVS3-48C allele arose from a single recent mutational event. Estimation of the age of the IVS3-48C allele from haplotype data in white and Asian populations yields an estimated age three to four times younger in the Japanese than in the white population, and this difference may be attributable either to differing demographic histories or to positive selection for the IVS3-48C allele in the Asian population. Finally, by calculating the KA/KS ratio in humans and chimpanzees, we show that the FECH protein sequence is subject to strong negative pressure. Overall, EPP looks like a Mendelian disorder, in which the prevalence of overt disease depends mainly on the frequency of a single common single-nucleotide polymorphism resulting from a unique mutational event that occurred 60,000 years ago.

Production and characterization of erythropoietic protoporphyric heterodimeric ferrochelatases

Mutations resulting in diminished activity of the dimeric enzyme ferrochelatase are a prerequisite for the inherited disorder erythropoietic protoporphyria (EPP). Patients with clinical EPP have only 10% to 30% of normal levels of ferrochelatase activity, and although many patients with EPP have one mutant allele and one "low-expression" normal allele, the possibility remains that, for some, low ferrochelatase activity may result from an EPP mutation that has an impact on both subunits of the wild-type/mutant heterodimer. Here we present data for 12 ferrochelatase wild-type/EPP mutant heterodimers showing that some mutations result in heterodimers with the residual activity anticipated from individual constituents, whereas others result in heterodimers with significantly lower activity than would be predicted. Although the data do not allow an a priori prediction of heterodimeric residual activity based solely on the in vitro activity of EPP homodimers or the position of the mutated residue within ferrochelatase, mutations that affect the dimer interface or [2Fe-2S] cluster have a significantly greater impact on residual activity than would be predicted. These data suggest that some EPP mutations may result in clinically overt EPP in the absence of a low-expression, wild-type allele; this is of potential significance for genetic counseling of patients with EPP.

A point mutation affecting an SP1 binding site in the promoter of the ferrochelatase gene impairs gene transcription and causes erythropoietic protoporphyria

OBJECTIVE

Clinical manifestation of erythropoietic protoporphyria (EPP) results from coinheritance of a mutated allele and a wild-type low-expressed allele of the ferrochelatase (FECH) gene. Currently, up to 90 different mutations affecting the coding region or splicing junctions of the FECH gene have been identified. Despite the high molecular heterogeneity, no functional mutations have been previously reported in the promoter region. The weaker allele expression has been controversially associated to the presence of different intragenic polymorphisms.

METHODS

We applied a two-step screening strategy using denaturing gradient gel electrophoresis followed by direct sequencing in order to rapidly identify FECH gene mutations in Italian EPP patients. We identified two unrelated subjects showing a normal FECH coding region but a single G>C base substitution at position -250 in the FECH promoter and the -251G, IVS1-23T, and IVS3-48C polymorphisms in trans to the substitution. To investigate the effect of the -250G>C mutation on protein binding to the FECH promoter, we conducted electro mobility shift assay (EMSA) and supershift analysis. To determine its effect on the transcriptional activity, K562 and Jurkat cell lines were transiently transfected.

RESULTS

EMSA showed that the -250G>C mutation results in the loss of an SP1 binding site, and transient transfection assays demonstrated that such mutation strongly impairs promoter activity. Moreover, we showed that the -251A>G polymorphism, although unable to affect SP1 binding, displays a significant reduction in the transcriptional activity of the promoter.

CONCLUSION

This is the first report of a mutation in the FECH promoter affecting binding of a transcription factor and causing EPP phenotype.

Ferrochelatase consisting of wild-type and mutated subunits from patients with a dominant-inherited disease, erythropoietic protoporphyria, is an active but unstable dimer

Erythropoietic protoporphyria (EPP) is an autosomal inherited disease of heme biosynthesis caused by a partial deficiency of the enzyme ferrochelatase. Patients with EPP show only 20-30% normal activity because of mutations in one of the alleles of the ferrochelatase gene. To clarify the molecular mechanisms of this low level of activity, we co-expressed human ferrochelatase carrying His- and HA-tags in a tandem fashion in Escherichia coli. Purification of the His-tag-containing enzyme revealed that the His-enzyme forms an oligomer in association with the HA-enzyme, and analysis by gel-filtration confirmed that the enzyme is a dimer (approximately 80 kDa). Then we expressed homo- and heterodimers composed of the wild-type and engineered mutants of the enzyme (C395Delta, H157A, H263A, H388A) or mutants from EPP patients (I186T, M267I). The levels of homodimeric enzymes produced were low, and the activities of the purified homodimeric mutants were abolished. On the other hand, the heterodimers with wild-type and mutated subunits exhibited potential, but weak, activities without a marked change of Km values for substrates. These results showed that heterodimers containing normal and mutated subunits retain the enzymic activity, which is inconsistent with the hypothesis that ferrochelatase is only active when the dimer contains two normal subunits. Pretreatment at 42 degrees C led to a rapid inactivation of the heterodimeric mutants, indicating instability. Thus, we provide evidence that the instability of the heterodimer containing normal and mutated ferrochelatase as well as the low production levels due to the structural defect of the mutant protein, not the abolishment of the enzymic activity of the heterodimer, causes the weak activity in EPP patients.

Hypermethylation of the wild-type ferrochelatase allele is closely associated with severe liver complication in a family with erythropoietic protoporphyria

Erythropoietic protoporphyria (EPP) is an inherited disorder of heme biosynthesis caused by cellular decreases in ferrochelatase (FECH) activity. Clinical expression of this disorder usually requires coinheritance of a mutant FECH allele and a normal FECH allele expressed at a low level. In this study, we investigated the methylation status of a normal, but poorly expressed, FECH gene in a single Japanese family with EPP. In this family, the proband died from liver failure, whereas the mother and sister exhibited overt EPP with mild liver dysfunction. A splicing mutation (IVS9+1g-->a) in the FECH gene, which produces a mutant FECH transcript lacking exon 9, was detected in the maternal allele of the proband and his sister. All subjects, including the father, who did not exhibit EPP, possessed the IVS3-48c/c genotype. This allele increases the proportion of aberrantly spliced mRNA, resulting in reduced FECH activity. Normal FECH transcripts were, however, detected in the mother and sister, but not in the proband. The CpG sites in the region from bases -78 to -31 were partially methylated in the proband and his father, but not in his mother or sister. Additionally, CpG methylation within this region reduced transcription of the FECH gene. These results suggest that whereas the combination of a maternal IVS9+1a allele and a paternal IVS3-48c allele results in overt EPP, CpG methylation of the FECH gene promoter, likely inherited from the father, increases the severity of EPP, leading to fatal liver failure, as seen in the proband.

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.

Genotypic determinants of phenotype in North American patients with erythropoietic protoporphyria

Erythropoietic protoporphyria (EPP) is characterized by excess accumulation of protoporphyrin, which is due to deficient activity of the enzyme ferrochelatase (FECH). This results in photosensitivity and in some patients liver disease which may necessitate liver transplantation. The aim of this study was to delineate the abnormalities in the FECH gene which cause phenotypic expression in EPP. We identified 43 individuals from 25 North American families with EPP who were heterozygous for various FECH mutations, but the mutations did not adequately explain the variable phenotype. We also examined the presence of an intron polymorphism (IVS3-48c) in the FECH gene which was shown to cause the formation of aberrantly spliced FECH mRNA. FECH DNA analysis demonstrated that 94% of 31 symptomatic individuals with FECH mutations were heterozygous for IVS3-48c, whereas 12 asymptomatic individuals with FECH mutations were homozygous for IVS3-48t. Haplotype analysis in four families showed that symptomatic members had the IVS3-48c polymorphism in the non-mutant FECH allele. Sequencing of the proximal FECH gene promoter showed no additional changes which might affect gene expression. The levels of normal FECH mRNA, measured by relative quantitative RT-PCR, and FECH enzyme activity were correspondingly lower in the cultured lymphoblasts of family members with the IVS3-48c polymorphism. These results indicate that symptomatic disease in most North American patients with EPP is explained by the inheritance of a mutation in one FECH allele which causes a structural alteration in the protein, together with a low expressing non-mutant FECH allele which is caused by the IVS3-48c polymorphism.

A "null allele" mutation is responsible for erythropoietic protoporphyria in an Israeli patient who underwent liver transplantation: relationships among biochemical, clinical, and genetic parameters

Mutations in the human ferrochelatase gene (FECH) are the primary cause of the inborn disorder erythropoietic protoporphyria (EPP). While the majority of the EPP patients exhibit only photosensitivity, a small percentage of patients (approximately 2%) develop liver complications in addition to the cutaneous symptoms. In this study, the FECH gene of an Israeli EPP patient who suffered from EPP-related liver complications was sequenced. A splicing defect IVS10+1, g-->t, which is known to cause the deletion of exon 10, was identified in the index patient as well as in his symptomatic older sister and his asymptomatic mother. Like the other 12 known FECH mutations associated with liver complications, IVS10+1, g-->t is a "null-allele" mutation. Although the two siblings with overt EPP share an identical genotype with respect to both the mutation on one FECH allele and three intragenic single nucleotide polymorphisms, -251G, IVS1-23T, and IVS3-48C on the other allele, the sister of the index patient has so far shown no signs of liver involvement, suggesting that additional factors might account for the liver disease in EPP.

Liver pathology and hepatocarcinogenesis in a long-term mouse model of erythropoietic protoporphyria

Erythropoietic protoporphyria (EPP) is an inherited disease of haem synthesis caused by a mutation in one of the alleles of the enzyme ferrochelatase. This mutation leads to partial deficiency of the enzyme, resulting in increased concentrations of protoporphyrin (PP) in blood, liver, and faeces. Five to ten per cent of patients with EPP develop severe liver disease characterized by the presence of PP deposits. This study used histochemistry and immunohistochemistry to investigate the histopathological features present in the livers of 44 mice with a heterozygous or homozygous point mutation in the ferrochelatase gene (fch/+ and fch/fch mice, respectively). Some fch/+ mouse livers showed mixed steatosis and large cell dysplasia. The livers of fch/fch mice showed periportal or septal fibrosis accompanied by an atypical ductular reaction. These findings suggest that the obstruction and damage of a proportion of large and small bile ducts by PP deposits cause an accumulation of PP in the parenchyma, which leads to damage and loss of hepatocytes due to the toxic effects of PP. The classical stages of hepatocarcinogenesis were observed and hepatic progenitor cells appear to be involved in this process. PP acts as the promoting agent and is probably also the initiating agent.

The genetics of inherited sideroblastic anemias

The sideroblastic anemias are a heterogeneous group of acquired and inherited bone marrow disorders defined by the presence of pathologic iron deposits in erythroblast mitochondria. While the pathogenesis of almost all cases of acquired sideroblastic anemia is unknown, the molecular genetic basis for several of the inherited forms have now been described. Initially, mutations in ALAS2 in X-linked sideroblastic anemia (XLSA) focused attention on the heme biosynthetic pathway as a primary cause of sideroblastic anemia. However, the subsequent description of the genes involved in XLSA with ataxia, thiamine-responsive megaloblastic anemia, and Pearson marrow-pancreas syndrome have implicated other pathways, including mitochondrial oxidative phosphorylation, thiamine metabolism, and iron-sulfur cluster biosynthesis, as primary defects in sideroblastic anemias that may only secondarily impact heme metabolism.

An exon 10 deletion in the mouse ferrochelatase gene has a dominant-negative effect and causes mild protoporphyria

Protoporphyria is generally inherited as an autosomal dominant disorder. The enzymatic defect of protoporphyria is a deficiency in ferrochelatase, which chelates iron and protoporphyrin IX to form heme. Patients with protoporphyria have decreased ferrochelatase activities that range from 5% to 30% of normal caused by heterogeneous mutations in the ferrochelatase gene. The molecular mechanism by which the ferrochelatase activity is decreased to less than an expected 50% is unresolved. In this study, we assessed the effect of a ferrochelatase exon 10 deletion, a common mutation in human protoporphyria, introduced into the mouse by gene targeting. F1 crosses produced (+/+), (+/-), and (-/-) mice at a ratio of 1:2:0; (-/-) embryos were detected at 3.5 days postcoitus, consistent with embryonic lethality for the homozygous mutant genotype. Heterozygotes demonstrated equivalent levels of wild-type and mutant ferrochelatase messenger RNAs and 2 immunoreactive proteins that corresponded to the full-length and an exon 10-deleted ferrochelatase protein. Ferrochelatase activities in the heterozygotes were an average of 37% of normal, and protoporphyrin levels were elevated in erythrocytes and bile. Heterozygous mice exhibited skin photosensitivity but no liver disease. These results lend support for a dominant-negative effect of a mutant allele on ferrochelatase activity in patients with protoporphyria.

Erythropoietic protoporphyria (EPP) at 40. Where are we now?

Since Professor Magnus first defined erythropoietic protoporphyria (EPP) in 1961, there has been considerable progress in the understanding this disease. The past decade has been a period of spectacular progress in understanding the genetics and pathogenesis of the disease by molecular investigation. However, progress in therapy for EPP has been slower, and has been dogged by difficulty in assessing treatment efficacy in patients. We are now entering an era in which advances in molecular genetics are directly affecting patient management. This review summarises laboratory and clinical progress in EPP in the past 40 years, and assesses the potential impact of molecular biology on clinical practice.

Erythropoietic protoporphyria: altered phenotype after bone marrow transplantation for myelogenous leukemia in a patient heteroallelic for ferrochelatase gene mutations

Acute myelogenous leukemia occurred in a 47-year-old woman whose 25-year history of cutaneous photosensitivity had been undiagnosed until abnormally high erythrocyte, plasma, and fecal protoporphyrin levels were discovered during evaluation for her hematologic disorder. She was found to be heteroallelic for ferrochelatase gene mutations, bearing a novel missense mutation caused by a C185-->G (Pro62-->Arg) transversion in exon 2 of one allele, and a previously described g-->a transition at the +5 position of the exon 1 donor site of the other allele, confirming a diagnosis of erythropoietic protoporphyria. Successful bone marrow transplantation from her brother, who is a mildly affected bearer of the second mutation, resulted in remission of the leukemia and in conversion of the protoporphyria phenotype of the recipient to one resembling that of the donor.

Haplotype analysis in determination of the heredity of erythropoietic protoporphyria among Swiss families

Defects in the human ferrochelatase gene lead to the hereditary disorder of erythropoietic protoporphyria. The clinical expression of this autosomal dominant disorder requires an allelic combination of a disabled mutant allele and a low-expressed nonmutant allele. Unlike most other erythropoietic protoporphyria populations, mutations identified among Swiss erythropoietic protoporphyria families to date have been relatively homogeneous. In this study, genotype analysis was conducted in seven Swiss erythropoietic protoporphyria families, three carrying mutation Q59X, two carrying mutation insT213, and two carrying mutation delTACAG(580-584). Three different haplotypes of five known intragenic single nucleotide polymorphisms, namely -251 A/G, IVS1-23C/T, 798 G/C, 921 A/G, and 1520C/T, were identified. Each haplotype was shared by families carrying an identical mutation in the ferrochelatase gene indicating a single mutation event for each of the three mutations. These mutations have been present in the Swiss erythropoietic protoporphyria population for a relatively long time as no common haplotypes of microsatellite markers flanking the ferrochelatase gene were found, except of two conserved regions, telomeric of the insT213 allele and centromeric of the delTACAG(580-584)allele, each with a size > 3 cM. Among the nonmutant ferrochelatase alleles, patients from six erythropoietic protoporphyria families shared a common haplotype [-251G; IVS1-23T] of the first two single nucleotide polymorphisms. An exception was the haplotype [-251 A; IVS1-23C] identified in the index patient of one erythropoietic protoporphyria family. These results supported the recent findings that the low expressed allele is tightly linked to a haplotype [-251G; IVS1-23T] of two intragenic single nucleotide polymorphisms in the ferrochelatase gene.