The acute porphyrias: a diagnostic and therapeutic challenge in internal and emergency medicine

The porphyrias are a heterogeneous group of metabolic diseases resulting from a variable catalytic defect of one of the eight enzymes involved in the heme biosynthesis pathway; they are mostly inherited diseases, but in some circumstances the metabolic disturbance may be acquired. The specific patterns of tissue overproduction (and hence accumulation and excretion) of toxic heme precursors, associated with each enzymatic deficiency, are responsible for the characteristic biochemical and clinical features of each of these diseases. Moreover, even in the presence of a specific inherited enzymatic defect, many different environmental factors (such as drugs, calorie restriction, hormones, sunlight exposition, infections, etc.) often play a key role in triggering the clinical expression of the various forms of porphyrias. The porphyrias are often misdiagnosed diseases, due their multiform clinical manifestations, able to mimic many other more common diseases. For this reason, many different specialists, such as surgeons, psychiatrists, gastroenterologists, neurologists, emergency physicians and dermatologists may be variably involved in the diagnostic process, especially for the forms presenting with acute and life-threatening clinical features. According to the clinical features, the porphyrias can be classified into neuropsychiatric (characterized by neurovisceral crises involving autonomic and central nervous system but also the liver and the kidney with possible consequences in terms of neurological, psychic, cardiac, respiratory, liver and kidney functions), dermatological (mostly presenting with cutaneous lesions due to photosensitivity), and mixed forms. From a strictly clinical point of view, porphyrias presenting with neurovisceral attacks are also referred as acute porphyrias: they are the object of the present review. An accurate diagnosis of acute porphyria requires knowledge and the use of correct diagnostic tools, and it is mandatory to provide a more appropriate therapeutic approach and prevent the use of potentially unsafe drugs, able to severely precipitate these diseases, especially in the presence of life-threatening symptoms. To date, availability of a relatively stable haem preparation (haem arginate) has significantly improved the treatment outcome of acute porphyric attacks, so the knowledge about the diagnosis and the management of these diseases may be relevant for physicians working in internal medicine, neurology and emergency units.     

Acute Hepatic Porphyria

The porphyrias comprise a set of diseases, each representing an individual defect in one of the eight enzymes mediating the pathway of heme synthesis. The diseases are genetically distinct but have in common the overproduction of heme precursors. In the case of the acute (neurologic) porphyrias, the cause of symptoms appears to be overproduction of a neurotoxic precursor. For the cutaneous porphyrias, it is photosensitizing porphyrins. Some types have both acute and cutaneous manifestations. The clinical presentation of acute porphyria consists of abdominal pain, nausea, and occasionally seizures. Only a small minority of those who carry a mutation for acute porphyria have pain attacks. The triggers for an acute attack encompass certain medications and severely decreased caloric intake. The propensity of females to acute attacks has been linked to internal changes in ovarian physiology. Symptoms are accompanied by large increases in delta-aminolevulinic acid and porphobilinogen in plasma and urine. Treatment of an acute attack centers initially on pain relief and elimination of inducing factors such as medications; glucose is administered to reverse the fasting state. The only specific treatment is administration of intravenous hemin. An important goal of treatment is preventing progression of the symptoms to a neurological crisis. Patients who progress despite hemin administration have undergone liver transplantation with complete resolution of symptoms. A current issue is the unavailability of a rapid test for urine porphobilinogen in the urgent-care setting.     

Porphyrien – was ist gesichert?

Porphyrias are caused by enzyme defects of heme biosynthesis. According to their clinical presentation and to each affected pathway, they are categorized into acute and non-acute as well as hepatic and erythropoietic porphyrias. Acute hepatic porphyrias, e.g. acute intermittent porphyria (AIP), porphyria variegata (VP), hereditary coproporphyria (HCP) and 5?aminolevulinic acid dehydratase-deficient porphyria (ALADP) are characterized by accumulation of the porphyrin precursors 5?aminolevulinic acid (ALA) and porphobilinogen (PBG) that correlate with severe abdominal, psychiatric, neurological or cardiovascular symptoms. Additionally, skin photosensitivity can occur in VP and less frequently, in HCP. Decisive for the diagnosis of acute hepatic porphyrias are a >4-fold elevated urinary excretion of ALA in ALADP and ALA and PBG in all other acute porphyrias. First-line treatment of an acute porphyria attack includes intensive care with pain management, sufficient caloric supply, strict avoidance of porphyrinogenic drugs and elimination of other triggering factors. Heme therapy is indispensable in case of developing neurological symptoms and clinical worsening despite first-line measures. Non-acute porphyrias, mainly porphyria cutanea tarda (PCT), erythropoietic protoporphyria (EPP) and X?linked protoporphyria (XLP) display accumulation of porphyrins in the skin and/or liver resulting in photosensitivity up to possible liver damage. Patients with PCT benefit from iron depletion, low-dose chloroquine treatment and/or hepatitis C virus elimination. Afamelanotide is associated with better sunlight tolerance in patients with EPP and XLP. Moreover, innovative therapies that highly selectively address dysregulated steps of the heme biosynthetic pathway are currently under clinical trial.     

Hepatic porphyria: A narrative review

Porphyrias are a group of metabolic disorders, which result from a specific abnormality in one of the eight enzymes of the heme biosynthetic pathway. These have been subdivided based on the predominant site of enzyme defect into hepatic and erythropoietic types and based on clinical presentation into acute neurovisceral and cutaneous blistering porphyrias. This review focuses on hepatic porphyrias, which include acute intermittent porphyria (AIP), variegate porphyria (VP), hereditary coproporphyria (HCP), aminolevulinic acid dehydratase deficiency porphyria (ADP), and porphyria cutanea tarda (PCT). Of these, AIP and ADP are classified as acute porphyria, PCT as cutaneous, while VP and HCP present with both acute and cutaneous clinical manifestations. Porphobilinogen levels in a spot urine sample is the initial screening test for the diagnosis of acute hepatic porphyria, and plasma with spot urine porphyrin levels is the initial screening test to approach patients suspected of cutaneous porphyria. Specific biochemical porphyrin profile for each porphyria helps in determining the specific diagnosis. Pain relief and elimination of triggering agents are the initial steps in managing a patient presenting with an acute attack. Intravenous glucose administration terminates the mild episode of acute porphyria, with intravenous hemin needed for management of moderate to severe episodes. Liver transplantation is curative and may be needed for patients with a life-threatening acute porphyria attack or for patients with recurrent acute attacks refractory to prophylactic treatment. Of the cutaneous porphyrias, PCT is the most common and is frequently associated with a combination of multiple susceptibility factors such as alcohol use, smoking, hepatitis C virus infection, HIV infection, estrogen use, and mutations of the hemochromatosis gene. Regular phlebotomy schedule and low-dose hydroxychloroquine are effective and safe treatment options for management of PCT.     

Porphyrias

Porphyrias are metabolic disorders of the heme biosynthesis. Clinically, they can be differentiated into acute and non-acute porphyrias. The symptomatic phase of acute hepatic porphyrias is characterized by overproduction of neurotoxic porphyrin precursors and porphyrins. Acute intermittent porphyria, Variegate porphyria, Hereditary coproporphyria and Doss porphyria belong to this group of metabolic disorders. The clinical presentation of the acute hepatic porphyria syndrome includes abdominal, psychiatric, neurological and cardiovascular symptoms. The diagnosis is based on a tenfold increased urinary excretion of porphobilinogen (apart from Doss porphyria). Besides symptomatic therapy with non-porphyrinogenic drugs, electrolyte compensation and intensive monitoring, intravenous administration of glucose and heme arginate is established for treatment. Among the non-acute types like Porphyria cutanea tarda, Erythropoietic protoporphyria and Congenital erythropoietic porphyria, the accumulated porphyrins cause photosensitivity of the skin up to severe liver damage. The location of the deficient enzyme within the heme biosynthesic pathway determines the pattern of the accumulated porphyrins. Besides light protection, there are different therapies depending on the type of non-acute porphyria. Ultimately, liver transplantation may be considered in therapy-resistant cases of acute hepatic porphyrias and bone marrow transplantation in severe cases of erythropoietic porphyrias.     

Porphyrien

Porphyrias are metabolic disorders of the heme biosynthesis. Clinically, they can be differentiated into acute and non-acute porphyrias. The symptomatic phase of acute hepatic porphyrias is characterized by overproduction of neurotoxic porphyrin precursors and porphyrins. Acute intermittent porphyria, Variegate porphyria, Hereditary coproporphyria and Doss porphyria belong to this group of metabolic disorders. The clinical presentation of the acute hepatic porphyria syndrome includes abdominal, psychiatric, neurological and cardiovascular symptoms. The diagnosis is based on a tenfold increased urinary excretion of porphobilinogen (apart from Doss porphyria). Besides symptomatic therapy with non-porphyrinogenic drugs, electrolyte compensation and intensive monitoring, intravenous administration of glucose and heme arginate is established for treatment. Among the non-acute types like Porphyria cutanea tarda, Erythropoietic protoporphyria and Congenital erythropoietic porphyria, the accumulated porphyrins cause photosensitivity of the skin up to severe liver damage. The location of the deficient enzyme within the heme biosynthesic pathway determines the pattern of the accumulated porphyrins. Besides light protection, there are different therapies depending on the type of non-acute porphyria. Ultimately, liver transplantation may be considered in therapy-resistant cases of acute hepatic porphyrias and bone marrow transplantation in severe cases of erythropoietic porphyrias.     

Postulated deficiency of hepatic heme and repair by hematin infusions in the "inducible" hepatic porphyrias.

There is compelling, indirect evidence of hepatic heme deficiency due primarily to the respective genetic errors of the three inducible hepatic porphyrias, acute intermittent porphyria, porphyria variegata, and hereditary coproporphyria. The induction is enhanced by exogenous inducers such as barbiturate, estrogens and other "porphyrogenic" chemicals and factors, including glucose deprivation. The newer knowledge of the induction of delta-aminolevulinic acid synthetase [delta-aminolevulinate synthase; succinyl--CoA:glycine C-succinyltransferase (decarboxylating), EC 2.3.1.37] in relation to inadequate heme, and repression by heme, stimulated early trials of hematin infusions to overcome the acute relapse in the foregoing inducible porphyrias. Recently this experience has been considerably expanded, 143 infusions of hematin having been given in 22 cases. Studies of the effect on the serum concentrations of delta-aminolevulinic acid and porphobilinogen have shown a highly significant decline, often to 0, especially of delta-aminolevulinic acid. A distinct relationship to the clinical severity of the attack has been evident in the frequency and magnitude of decline of serum delta-aminolevulinic acid and porphobilinogen. This was regularly associated with objective clinical improvement.     

Molecular mechanisms of dominant expression in porphyria

Summary Summary:#Partial deficiency of enzymes in the haem synthetic pathway gives rise to a group of seven inherited metabolic disorders, the porphyrias. Each deficiency is associated with a characteristic increase in haem precursors that correlates with the symptoms associated with individual porphyrias and allows accurate diagnosis. Two types of clinical presentation occur separately or in combination; acute life-threatening neurovisceral attacks and/or cutaneous symptoms. Five of the porphyrias are low-penetrance autosomal dominant conditions in which clinical expression results from additional factors that act by increasing demand for haem or by causing an additional decrease in enzyme activity or by a combination of these effects. These include both genetic and environmental factors. In familial porphyria cutanea tarda (PCTF), environmental factors that include alcohol, exogenous oestrogens and hepatotropic viruses result in inhibition of hepatic enzyme activity via a mechanism that involves excess iron accumulation. In erythropoietic protoporphyria (EPP), co-inheritance of a functional polymorphism in trans to a null ferrochelatase allele accounts for most clinically overt cases. In the autosomal dominant acute hepatic porphyrias (acute intermittent porphyria, variegate porphyria, hereditary coproporphyria), acute neurovisceral attacks occur in a minority of those who inherit one of these disorders. Although various exogenous (e.g. drugs, alcohol) and endogenous factors (e.g. hormones) have been identified as provoking acute attacks, these do not provide a full explanation for the low penetrance of these disorders. It seems probable that genetic background influences susceptibility to acute attacks, but the genes that are involved have not yet been identified.     

The acute hepatic porphyrias: current status and future challenges

The porphyrias are predominantly inherited metabolic disorders, which result from a specific deficiency of one of the eight enzymes along the pathway of haem biosynthesis. Historically, they have been classified into hepatic and erythropoietic forms, based on the primary site of expression of the prevailing dysfunctional enzyme. From a clinical point of view, however, it is more convenient to subdivide them into acute and non-acute porphyrias, thereby primarily considering the potential occurrence of life-threatening acute neurovisceral attacks. Unrecognised or untreated, such an acute porphyric attack is associated with a significant mortality of up to 10%. The acute hepatic porphyrias comprise acute intermittent porphyria, variegate porphyria, hereditary coproporphyria, and δ-aminolevulinic acid dehydratase deficiency porphyria. Making a precise diagnosis may be difficult because the different types of porphyrias may show overlapping clinical and biochemical characteristics. To date, the therapeutic possibilities are limited and mainly symptomatic. In this overview we report on what is currently known about pathogenesis, clinic, diagnostics, and therapy of the acute hepatic porphyrias. We further point out actual and future challenges in the management of these diseases.     

A challenging diagnosis for potential fatal diseases: Recommendations for diagnosing acute porphyrias

Acute porphyrias are a heterogeneous group of metabolic disorders resulting from a variable catalytic defect of four enzymes out of the eight involved in the haem biosynthesis pathway; they are rare and mostly inherited diseases, but in some circumstances, the metabolic disturbance may be acquired. Many different environmental factors or pathological conditions (such as drugs, calorie restriction, hormones, infections, or alcohol abuse) often play a key role in triggering the clinical exacerbation (acute porphyric attack) of these diseases that may often mimic many other more common acute medical and neuropsychiatric conditions and whose delayed diagnosis and treatment may be fatal. In order to obtain an accurate diagnosis of acute porphyria, the knowledge and the use of appropriate diagnostic tools are mandatory, even in order to provide as soon as possible the more effective treatment and to prevent the use of potentially unsafe drugs, which can severely precipitate these diseases, especially in the presence of life-threatening symptoms.In this paper, we provide some recommendations for the diagnostic steps of acute porphyrias by reviewing literature and referring to clinical experience of the board members of the Gruppo Italiano Porfiria (GrIP).     

Hepatic porphyrias: diagnosis and management

Porphyrias are a group of metabolic disorders in which there are defects in the normal pathway for the biosynthesis of heme, the critical prosthetic group for numerous hemoproteins. The clinical manifestations of the porphyrias can be highly varied, and patients may present to general physicians and be referred to a wide variety of subspecialists because of these manifestations. However, two major clinical forms are represented by the so-called "acute" porphyrias, in which patients suffer recurrent bouts of pain, especially pain in the abdomen, and the "cutaneous" porphyrias, in which patients have painful skin lesions. Knowledge of the factors chiefly responsible for regulating the rate of synthesis of heme has helped to explain how drugs and other factors may cause porphyria. Knowledge of the physical and chemical properties of porphyrins also forms an important part of the foundation for understanding the clinical manifestations of these diseases. Thus, the porphyrias can best be understood after reviewing the chemical properties of porphyrins and heme and the control of their biosynthesis.     

Hepatic porphyrias

The porphyrias are metabolic disorders characterized by abnormal heme biosynthesis with excessive accumulation and excretion of porphyrias or porphyrin precursors. Defects in the enzymes of the heme biosynthetic pathway result in porphyria. Several of the disorders have been classified as hepatic because the major site of the biochemical defect has been localized to the liver. This article describes the enzymes of the heme biosynthetic pathway, the clinical features of the hepatic porphyrias and management of the disorders.     

Treatment options in acute porphyria,porphyria cutanea tarda,and erythropoietic protoporphyria

Opinion statement The porphyrias are a group of uncommon metabolic diseases caused by enzyme deficiencies within heme biosynthesis that lead to neurotoxic or phototoxic heme precursor accumulation. There are four acute porphyrias characterized by neuropsy-chiatric symptoms: acute intermittent porphyria, variegate porphyria, hereditary coproporphyria, and 5-aminolevulinic acid dehydratase deficiency porphyria. Treatment includes elimination of any porphyrogenic factor and symptomatic treatment. Carbohydrate and intravenous heme administration constitute specific therapies in the disorders’ acute phase. The mainstay treatment in the cutaneous porphyrias is avoidance of sunlight exposure. In porphyria cutanea tarda and the two acute porphyrias with skin manifestations, variegate porphyria and hereditary coproporphyria, care of the vulnerable skin is important. In porphyria cutanea tarda, specific treatment is accomplished by a series of phlebotomies and/or by low-dose chloroquine administration. In erythropoietic protoporphyria, light-protective beta-carotene is prescribed.     

Porphyrias

Seven different porphyrias form a group of inherited metabolic disorders, each resulting from a partial deficiency of a specific enzyme in the haem biosynthesis pathway. Clinically, the three most important entities are an acute porphyric attack and acute and chronic skin symptoms. Porphyrias are rare and sometimes misdiagnosed, because various symptoms and signs mimic other diseases. Once porphyria is suspected, biochemical analyses easily detect porphyrins and their precursors from blood, urine, or faeces. Mutation screening can be done at the quiescent phase of the disease. Pathogenetic mechanisms and clinical manifestations differ in individual porphyrias and most of them require a specific treatment. Early diagnosis and information about precipitating factors can diminish mortality and prevent subsequent attacks among patients with acute porphyrias, so mutation screening is recommended for family members.     

Heme arginate: effects on hemostasis

Hematin, the drug used for acute porphyric attacks, has been shown to cause disturbances in hemostasis, mainly because of its degradation products. Lately a new heme compound, heme arginate, has been developed for the treatment of porphyrias. In experimental animal studies as well as in clinical use it has proved to be well tolerated. To find out whether heme arginate has any effects on hemostasis we have studied a number of parameters of coagulation and fibrinolysis after a heme arginate infusion in seven healthy volunteers. All parameters studied remained practically unchanged except the coagulation factor X, which showed a transient, insignificant decrease during the maximal heme concentration. We believe that the lack of side effects is due to a better stability of heme arginate, the degradation rates being 1% for heme arginate and 61% for hematin in four hours. Our data favor the use of heme arginate in acute porphyrias as well as in other deficiency states of heme.     

Recommendations for the diagnosis and treatment of the acute porphyrias

The acute porphyrias, 4 inherited disorders of heme biosynthesis, cause life-threatening attacks of neurovisceral symptoms that mimic many other acute medical and psychiatric conditions. Lack of clinical recognition often delays effective treatment, and inappropriate diagnostic tests may lead to misdiagnosis and inappropriate treatment. We review the clinical manifestations, pathophysiology, and genetics of the acute porphyrias and provide recommendations for diagnosis and treatment on the basis of reviews of the literature and clinical experience. An acute porphyria should be considered in many patients with unexplained abdominal pain or other characteristic symptoms. The diagnosis can be rapidly confirmed by demonstration of a markedly increased urinary porphobilinogen level by using a single-void urine specimen. This specimen should also be saved for quantitative measurement of porphobilinogen, 5-aminolevulinic acid, and total porphyrin levels. Intravenous hemin therapy, started as soon as possible, is the most effective treatment. Intravenous glucose alone is appropriate only for mild attacks (mild pain, no paresis or hyponatremia) or until hemin is available. Precipitating factors should be eliminated, and appropriate supportive and symptomatic therapy should be initiated. Prompt diagnosis and treatment greatly improve prognosis and may prevent development of severe or chronic neuropathic symptoms. We recommend identification of at-risk relatives through enzymatic or gene studies.     

Hepatic porphyria]

INTRODUCTION: This review is aimed at presenting classification and diagnosis criteria of hepatic porphyrias and at proposing guidelines for diagnosis and management of these diseases. CURRENT KNOWLEDGE AND KEY POINTS: Porphyrias are inherited disorders: each type of porphyria is the result of a specific decrease in the activity of one of the enzymes of heme biosynthesis. Porphyrias are presently classified as erythropoietic or hepatic, depending on the primary organ in which excess production of porphyrins or precursors takes place. From 1970 to 1998, there have been important advances in the understanding of these diseases: specific enzyme deficiencies have been demonstrated, and genes have been isolated and located. These advances have been followed rapidly by identification of mutations. PERSPECTIVES AND PROJECTS: Treatment of acute attacks by hematin completely changed the disease prognosis. Relationships between porphyria cutanea tarda and hepatitis C virus or hemochromatosis have also been clarified. However, several important issues are still not solved: for instance, pathogenesis of neuronal dysfunction that produces the acute attacks is poorly understood. Differences related to susceptibility to develop acute attacks are not known.     

The porphyrias.

The heterogeneous group of diseases called the porphyrias may all be characterised by derangement of specific stages in the haem biosynthetic pathway. In the acute porphyrias; acute intermittent porphyria, urophorphyrinogen 1 synthase, hereditary coproporphyria, coproporphyrinogen oxidase and variegate porphyria, ferrochelatase or protoporphyrinogen oxidase, are the enzymes affected, whilst in the non acute porphyrias, cutaneous hepatic porphyria, uroporphyrinogen decarboxylase, congenital porphyria, uroporphyrinogen cosynthase; and erythropoietic protoporphyria; ferrochelatase are the enzymes affected. In each of the porphyrias, the activity of the initial and rate controlling enzyme of the pathway, delta-aminolaevulinic acid synthase is raised which constitutes the principal control point of the pathway. Secondary control in each of these diseases lies at the leve of uroporphyrinogen 1 synthase. As a consequence of this secondary control, there is excessive excretion of the porphyrin precursors delta-aminolaevulinic acid and porphobilinogen in the acute porphyrias and excessive excretion of porphyrins leading to solar photosensitivity in the non-acute porphyrias and in variegate and hereditary coproporphyria. There are a number of secondary metabolic aspects in the porphyrias, such as the role of steroid metabolism; the influence of drugs in the potentiation of attacks; and the potential for the pathway to branch at stages prior to porphyrin formation which result in the synthesis of various monopyrroles. The therapy of the two groups of porphyrias are quite different. Prophylaxis is important in both types but is particularly important in the avoidance of various drugs in the acute porphyrias. The acute attack may be specifically treated with carbohydrates, beta-blockers and haematin. Cutaneous hepatic porphyria may be treated by venesection, erythropoietic protoporphyria with beta caratene whilst congenital porphyria may be improved by splenectomy and chloroquine therapy.     

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.