European Specialist Porphyria Laboratories: Diagnostic Strategies, Analytical Quality, Clinical Interpretation, and Reporting As Assessed by an External Quality Assurance Program

BACKGROUND: The porphyrias are a group of rare metabolic disorders whose diagnosis depends on identification of specific patterns of porphyrin precursor and porphyrin accumulation in urine, blood, and feces. Diagnostic tests for porphyria are performed by specialized laboratories in many countries. Data regarding the analytical and diagnostic performance of these laboratories are scarce. METHODS: We distributed 5 sets of multispecimen samples from different porphyria patients accompanied by clinical case histories to 18–21 European specialist porphyria laboratories/centers as part of a European Porphyria Network organized external analytical and postanalytical quality assessment (EQA) program. The laboratories stated which analyses they would normally have performed given the case histories and reported results of all porphyria-related analyses available, interpretative comments, and diagnoses. RESULTS: Reported diagnostic strategies initially showed considerable diversity, but the number of laboratories applying adequate diagnostic strategies increased during the study period. We found an average interlaboratory CV of 50% (range 12%–152%) for analytes in absolute concentrations. Result normalization by forming ratios to the upper reference limits did not reduce this variation. Sixty-five percent of reported results were within biological variation–based analytical quality specifications. Clinical interpretation of the obtained analytical results was accurate, and most laboratories established the correct diagnosis in all distributions. CONCLUSIONS: Based on a case-based EQA scheme, variations were apparent in analytical and diagnostic performance between European specialist porphyria laboratories. Our findings reinforce the use of EQA schemes as an essential tool to assess both analytical and diagnostic processes and thereby to improve patient care in rare diseases

Acute intermittent porphyria causes hepatic mitochondrial energetic failure in a mouse model

Acute intermittent porphyria (AIP), an inherited hepatic disorder, is due to a defect of hydroxymethylbilane synthase (HMBS), an enzyme involved in heme biosynthesis. AIP is characterized by recurrent, life-threatening attacks at least partly due to the increased hepatic production of 5-aminolaevulinic acid (ALA). Both the mitochondrial enzyme, ALA synthase (ALAS) 1, involved in the first step of heme biosynthesis, which is closely linked to mitochondrial bioenergetic pathways, and the promise of an ALAS1 siRNA hepatic therapy in humans, led us to investigate hepatic energetic metabolism in Hmbs KO mice treated with phenobarbital. The mitochondrial respiratory chain (RC) and the tricarboxylic acid (TCA) cycle were explored in the Hmbs−/− mouse model. RC and TCA cycle were significantly affected in comparison to controls in mice treated with phenobarbital with decreased activities of RC complexes I (−52%, **p < 0.01), II (−50%, **p < 0.01) and III (−55%, *p < 0.05), and decreased activity of α-ketoglutarate dehydrogenase (−64%, *p < 0.05), citrate synthase (−48%, **p < 0.01) and succinate dehydrogenase (−53%, *p < 0.05). Complex II-driven succinate respiration was also significantly affected. Most of these metabolic alterations were at least partially restored after the phenobarbital arrest and heme arginate administration. These results suggest a cataplerosis of the TCA cycle induced by phenobarbital, caused by the massive withdrawal of succinyl-CoA by ALAS induction, such that the TCA cycle is unable to supply the reduced cofactors to the RC. This profound and reversible impact of AIP on mitochondrial energetic metabolism offers new insights into the beneficial effect of heme, glucose and ALAS1 siRNA treatments by limiting the cataplerosis of TCA cycle

Mitochondrial energetic defects in muscle and brain of a Hmbs-/- mouse model of acute intermittent porphyria

Acute intermittent porphyria (AIP), an autosomal dominant metabolic disease (MIM #176000), is due to a deficiency of hydroxymethylbilane synthase (HMBS), which catalyzes the third step of the heme biosynthetic pathway. The clinical expression of the disease is mainly neurological, involving the autonomous, central and peripheral nervous systems. We explored mitochondrial oxidative phosphorylation (OXPHOS) in the brain and skeletal muscle of the Hmbs(-/-) mouse model first in the basal state (BS), and then after induction of the disease with phenobarbital and treatment with heme arginate (HA). The modification of the respiratory parameters, determined in mice in the BS, reflected a spontaneous metabolic energetic adaptation to HMBS deficiency. Phenobarbital induced a sharp alteration of the oxidative metabolism with a significant decrease of ATP production in skeletal muscle that was restored by treatment with HA. This OXPHOS defect was due to deficiencies in complexes I and II in the skeletal muscle whereas all four respiratory chain complexes were affected in the brain. To date, the pathogenesis of AIP has been mainly attributed to the neurotoxicity of aminolevulinic acid and heme deficiency. Our results show that mitochondrial energetic failure also plays an important role in the expression of the disease

Key Terms and Definitions in Acute Porphyrias: Results of an International Delphi Consensus Led by the European Porphyria Network

Background: Acute porphyrias are a group of rare inherited disorders causing acute neurovisceral attacks. Many terms used frequently in the literature and in clinical practice are ambiguous, which can lead to confusion in the way patients are managed, studied, and reported in clinical studies. Agreed definitions are a necessary first step in developing management guidelines and will facilitate communication of results of future clinical research. Methods: The Delphi method was used to generate consensus on key terms and definitions in acute porphyria. The process started with a brainstorming phase offered to all members of the European Porphyria Network followed by 2 Delphi rounds among international experts in the field of porphyria (the Acute Porphyria Expert Panel). A consensus of 75% or more was defined as the agreement threshold. Results: 63 respondents from 26 countries participated in the brainstorming phase, leading to the choice of 9 terms and definitions. 34 experts were invited to take part in the Delphi rounds. 7 of the initial 9 terms and definitions which entered the first Delphi round achieved the threshold for agreement. Following a second Delphi round, all 9 definitions achieved agreement. Conclusion: Agreement on the definitions for 9 important terms describing acute porphyrias represents a significant step forward for the porphyria community. It will facilitate more accurate comparison of outcomes among porphyria centres and in clinical trials and provide a strong framework for developing evidence based clinical guidelines.Background: Acute porphyrias are a group of rare inherited disorders causing acute neurovisceral attacks. Many terms used frequently in the literature and in clinical practice are ambiguous, which can lead to confusion in the way patients are managed, studied, and reported in clinical studies. Agreed definitions are a necessary first step in developing management guidelines and will facilitate communication of results of future clinical research. Methods: The Delphi method was used to generate consensus on key terms and definitions in acute porphyria. The process started with a brainstorming phase offered to all members of the European Porphyria Network followed by 2 Delphi rounds among international experts in the field of porphyria (the Acute Porphyria Expert Panel). A consensus of 75% or more was defined as the agreement threshold. Results: 63 respondents from 26 countries participated in the brainstorming phase, leading to the choice of 9 terms and definitions. 34 experts were invited to take part in the Delphi rounds. 7 of the initial 9 terms and definitions which entered the first Delphi round achieved the threshold for agreement. Following a second Delphi round, all 9 definitions achieved agreement. Conclusion: Agreement on the definitions for 9 important terms describing acute porphyrias represents a significant step forward for the porphyria community. It will facilitate more accurate comparison of outcomes among porphyria centres and in clinical trials and provide a strong framework for developing evidence based clinical guidelines

EXPLORE: A Prospective, Multinational, Natural History Study of Patients with Acute Hepatic Porphyria with Recurrent Attacks

BACKGROUND AND AIMS: Acute hepatic porphyria comprises a group of rare genetic diseases caused by mutations in genes involved in heme biosynthesis. Patients can experience acute neurovisceral attacks, debilitating chronic symptoms, and long-term complications. There is a lack of multinational, prospective data characterizing the disease and current treatment practices in severely affected patients. APPROACH AND RESULTS: EXPLORE is a prospective, multinational, natural history study characterizing disease activity and clinical management in patients with acute hepatic porphyria who experience recurrent attacks. Eligible patients had a confirmed acute hepatic porphyria diagnosis and had experienced ≥3 attacks in the prior 12 months or were receiving prophylactic treatment. A total of 112 patients were enrolled and followed for at least 6 months. In the 12 months before the study, patients reported a median (range) of 6 (0-52) acute attacks, with 52 (46%) patients receiving hemin prophylaxis. Chronic symptoms were reported by 73 (65%) patients, with 52 (46%) patients experiencing these daily. During the study, 98 (88%) patients experienced a total of 483 attacks, 77% of which required treatment at a health care facility and/or hemin administration (median [range] annualized attack rate 2.0 [0.0-37.0]). Elevated levels of hepatic δ-aminolevulinic acid synthase 1 messenger ribonucleic acid levels, δ-aminolevulinic acid, and porphobilinogen compared with the upper limit of normal in healthy individuals were observed at baseline and increased further during attacks. Patients had impaired quality of life and increased health care utilization. CONCLUSIONS: Patients experienced attacks often requiring treatment in a health care facility and/or with hemin, as well as chronic symptoms that adversely influenced day-to-day functioning. In this patient group, the high disease burden and diminished quality of life highlight the need for novel therapies. (Hepatology 2020;71:1546-1558)

EXPLORE: A prospective, multinational natural history study of patients with acute hepatic porphyria with recurrent attacks

BACKGROUND AND AIMS: Acute hepatic porphyria comprises a group of rare genetic diseases caused by mutations in genes involved in heme biosynthesis. Patients can experience acute neurovisceral attacks, debilitating chronic symptoms, and long-term complications. There is a lack of multinational, prospective data characterizing the disease and current treatment practices in severely affected patients. APPROACH AND RESULTS: EXPLORE is a prospective, multinational, natural history study characterizing disease activity and clinical management in patients with acute hepatic porphyria who experience recurrent attacks. Eligible patients had a confirmed acute hepatic porphyria diagnosis and had experienced ≥3 attacks in the prior 12 months or were receiving prophylactic treatment. A total of 112 patients were enrolled and followed for at least 6 months. In the 12 months before the study, patients reported a median (range) of 6 (0-52) acute attacks, with 52 (46%) patients receiving hemin prophylaxis. Chronic symptoms were reported by 73 (65%) patients, with 52 (46%) patients experiencing these daily. During the study, 98 (88%) patients experienced a total of 483 attacks, 77% of which required treatment at a health care facility and/or hemin administration (median [range] annualized attack rate 2.0 [0.0-37.0]). Elevated levels of hepatic δ-aminolevulinic acid synthase 1 messenger ribonucleic acid levels, δ-aminolevulinic acid, and porphobilinogen compared with the upper limit of normal in healthy individuals were observed at baseline and increased further during attacks. Patients had impaired quality of life and increased health care utilization. CONCLUSIONS: Patients experienced attacks often requiring treatment in a health care facility and/or with hemin, as well as chronic symptoms that adversely influenced day-to-day functioning. In this patient group, the high disease burden and diminished quality of life highlight the need for novel therapies. (Hepatology 2020;71:1546-1558)

EXPLORE: A Prospective, Multinational, Natural History Study of Patients with Acute Hepatic Porphyria with Recurrent Attacks

Abstract Acute hepatic porphyria comprises a group of rare, genetic diseases caused by mutations in genes involved in heme biosynthesis. Patients can experience acute neurovisceral attacks, debilitating chronic symptoms, and long-term complications. There is a lack of multinational, prospective data characterizing the disease and current treatment practices in severely affected patients. EXPLORE is a prospective, multinational, natural history study characterizing disease activity and clinical management in patients with acute hepatic porphyria who experience recurrent attacks. Eligible patients had a confirmed acute hepatic porphyria diagnosis and had experienced ≥3 attacks in the prior 12 months or were receiving prophylactic treatment. A total of 112 patients were enrolled and followed for at least 6 months. In the 12 months prior to the study, patients reported a median (range) of 6 (0-52) acute attacks, with 52 (46%) patients receiving hemin prophylaxis. Chronic symptoms were reported by 73 (65%) patients, with 52 (46%) patients experiencing these daily. During the study, 98 (88%) patients experienced a total of 483 attacks, 77% of which required treatment at a healthcare facility and/or hemin administration (median [range] annualized attack rate 2.0 [0.0-37.0]). Elevated levels of hepatic δ-aminolevulinic acid synthase 1 messenger ribonucleic acid levels, δ-aminolevulinic acid, and porphobilinogen compared with the upper limit of normal in healthy individuals were observed at baseline and increased further during attacks. Patients had impaired quality of life and increased healthcare utilization. Conclusions: Patients experienced attacks often requiring treatment in a healthcare facility and/or with hemin, as well as chronic symptoms that adversely influence day-to-day functioning. In this patient group, the high disease burden and diminished quality of life highlight the need for novel therapies. This article is protected by copyright. All rights reserved.Peer reviewe

Recurrent attacks of acute hepatic porphyria: major role of the chronic inflammatory response in the liver

[Background] Acute intermittent porphyria (AIP) is an inherited disorder of haem metabolism characterized by life‐threatening acute neurovisceral attacks due to the induction of hepatic δ‐aminolevulinic acid synthase 1 (ALAS1) associated with hydroxymethylbilane synthase (HMBS) deficiency. So far, the treatment of choice is hemin which represses ALAS1. The main issue in the medical care of AIP patients is the occurrence of debilitating recurrent attacks. [Objective] The aim of this study was to determine whether chronic hemin administration contributes to the recurrence of acute attacks. [Methods] A follow‐up study was conducted between 1974 and 2015 and included 602 French AIP patients, of whom 46 had recurrent AIP. Moreover, we studied the hepatic transcriptome, serum proteome, liver macrophage polarization and oxidative and inflammatory profiles of Hmbs−/− mice chronically treated by hemin and extended the investigations to five explanted livers from recurrent AIP patients. [Results] The introduction of hemin into the pharmacopeia has coincided with a 4.4‐fold increase in the prevalence of chronic patients. Moreover, we showed that both in animal model and in human liver, frequent hemin infusions generate a chronic inflammatory hepatic disease which induces HO1 remotely to hemin treatment and maintains a high ALAS1 level responsible for recurrence. [Conclusion] Altogether, this study has important impacts on AIP care underlying that hemin needs to be restricted to severe neurovisceral crisis and suggests that alternative treatment targeting the liver such as ALAS1 and HO1 inhibitors, and anti‐inflammatory therapies should be considered in patients with recurrent AIP.LG, JCD, PH, ES and AKA were funded for attending meeting related to ongoing clinical trial by Alnylam Pharmaceuticals.Peer reviewe

Erythropoietic protoporphyria

Erythropoietic protoporphyria (EPP) is an inherited disorder of the haem metabolic pathway characterised by accumulation of protoporphyrin in blood, erythrocytes and tissues, and cutaneous manifestations of photosensitivity. EPP has been reported worldwide, with prevalence between 1:75,000 and 1:200,000. It usually manifests in early infancy upon the first sun exposures. EPP is characterised by cutaneous manifestations of acute painful photosensitivity with erythema and oedema, sometimes with petechiae, together with stinging and burning sensations upon exposure to sunlight, without blisters. These episodes have a variable severity depending on the exposure duration and may result in chronic permanent lesions on exposed skin. As protoporphyrin is a lipophilic molecule that is excreted by the liver, EPP patients are at risk of cholelithiasis with obstructive episodes, and chronic liver disease that might evolve to rapid acute liver failure. In most patients, EPP results from a partial deficiency of the last enzyme of the haem biosynthetic pathway, ferrochelatase, EC 4.99.1.1/FECH (encoded by the FECH gene). EPP appears to be inherited as an autosomal dominant disease, the clinical expression of which is modulated by the presence of the hypomorphic FECH IVS3-48C allele trans, but recessive inheritance with two mutated FECH alleles has also been described. In about 2% of patients, overt disease was recently shown to be caused by gain-of-function mutations in the erythroid-specific aminolevulinic acid synthase 2 (ALAS2/ALAS, EC 2.3.1.27) gene and named X-linked dominant protoporphyria. Diagnosis is established by finding increased levels of protoporphyrin in plasma and red blood cells, and detection of a plasma fluorescence peak at 634 nm. Investigations for hepatic involvement, ferrochelatase activity level, genetic analysis (FECH mutations, presence of the hypomorphic FECH IVS3-48C allele trans and ALAS2 mutations) and family studies are advisable. Differential diagnosis includes phototoxic drug reactions, hydroa vacciniforme, solar urticaria, contact dermatitis, angio-oedema and, in some cases, other types of porphyria. Management includes avoidance of exposure to light, reduction of protoporphyrin levels and prevention of progression of possible liver disease to liver failure. As the major risk in EPP patients is liver disease, a regular follow-up of hepatic involvement is essential. Sequential hepatic and bone marrow transplantation should be considered as a suitable treatment for most severe cases of EPP with hepatic involvement. EPP is a lifelong disorder whose prognosis depends on the evolution of the hepatic disease. However, photosensitivity may have a significant impact on quality of life of EPP patients

Recurrent attacks of acute hepatic porphyria: major role of the chronic inflammatory response in the liver

Acute intermittent porphyria (AIP) is an inherited disorder of heme metabolism characterized by life-threatening acute neurovisceral attacks due to the induction of hepatic -aminolevulinic acid synthase 1 (ALAS1) associated with hydroxymethylbilane synthase (HMBS) deficiency. Hemin represses ALAS1 and restores metabolic equilibrium. The main issue in the medical care of AIP patients is the occurrence of debilitating recurrent attacks. Chronically ill patients require repeated hemin infusions and develop secondary hemochromatosis and have a poorer quality of life. To decipher the mechanisms underlying recurrence in AIP patients, we studied the metabolic pathways altered by chronic hemin administration. A follow-up study was conducted between 1974 and 2015 and included 602 French AIP patients, of whom 46 had recurrent AIP. Moreover, we studied the hepatic transcriptome, serum proteome, liver macrophage polarization and oxidative and inflammatory profiles of Hmbs-/- mice chronically treated by hemin and extended the investigations to 5 human explanted livers. The introduction of hemin into the pharmacopeia has coincided with a 4.4-fold increase in the prevalence of chronic patients. We show that repeated hemin infusions trigger a high level heme oxygenase 1 (HO1) response, induce a pro-oxidative iron accumulation and a complex pattern of liver inflammation with macrophage infiltration. Conclusion: chronically heme-treated AIP patients may present with symptoms of an inflammatory disease responsible for an adaptive HO1 induction that could deplete the free heme pool inducing ALAS1. Hemin remains the most effective treatment but should be restricted to patients with severe forms of AIP to prevent chronic damage