Heme biosynthesis and the porphyrias

Porphyrias, is a general term for a group of metabolic diseases that are genetic in nature. In each specific porphyria the activity of specific enzymes in the heme biosynthetic pathway is defective and leads to accumulation of pathway intermediates. Phenotypically, each disease leads to either neurologic and/or photocutaneous symptoms based on the metabolic intermediate that accumulates. In each porphyria the distinct patterns of these substances in plasma, erythrocytes, urine and feces are the basis for diagnostically defining the metabolic defect underlying the clinical observations. Porphyrias may also be classified as either erythropoietic or hepatic, depending on the principal site of accumulation of pathway intermediates. The erythropoietic porphyrias are congenital erythropoietic porphyria (CEP), and erythropoietic protoporphyria (EPP). The acute hepatic porphyrias include ALA dehydratase deficiency porphyria, acute intermittent porphyria (AIP), hereditary coproporphyria (HCP) and variegate porphyria (VP). Porphyria cutanea tarda (PCT) is the only porphyria that has both genetic and/or environmental factors that lead to reduced activity of uroporphyrinogen decarboxylase in the liver. Each of the 8 enzymes in the heme biosynthetic pathway have been associated with a specific porphyria (Table 1). Mutations affecting the erythroid form of ALA synthase (ALAS2) are most commonly associated with X-linked sideroblastic anemia, however, gain-of-function mutations of ALAS2 have also been associated with a variant form of EPP. This overview does not describe the full clinical spectrum of the porphyrias, but is meant to be an overview of the biochemical steps that are required to make heme in both erythroid and non-erythroid cells.

Recent advances on porphyria genetics: Inheritance, penetrance & molecular heterogeneity, including new modifying/causative genes

The inborn errors of heme biosynthesis, the Porphyrias, include eight major disorders resulting from loss-of-function (LOF) or gain-of-function (GOF) mutations in eight of the nine heme biosynthetic genes. The major sites of heme biosynthesis are the liver and erythron, and the underlying pathophysiology of each of these disorders depends on the unique biochemistry, cell biology, and genetic mechanisms in these tissues. The porphyrias are classified into three major categories: 1) the acute hepatic porphyrias (AHPs), including Acute Intermittent Porphyria (AIP), Hereditary Coproporphyria (HCP), Variegate Porphyria (VP), and 5-Aminolevlulinic Acid Dehydratase Deficient Porphyria (ADP); 2) a hepatic cutaneous porphyria, Porphyria Cutanea Tarda (PCT); and 3) the cutaneous erythropoietic porphyrias, Congenital Erythropoietic Porphyria (CEP), Erythropoietic Protoporphyria (EPP), and X-Linked Protoporphyria (XLP). Their modes of inheritance include autosomal dominant with markedly decreased penetrance (AIP, VP, and HCP), autosomal recessive (ADP, CEP, and EPP), or X-linked (XLP), as well as an acquired sporadic form (PCT). There are severe homozygous dominant forms of the three AHPs. For each porphyria, its phenotype, inheritance pattern, unique genetic principles, and molecular genetic heterogeneity are presented. To date, >1000 mutations in the heme biosynthetic genes causing their respective porphyrias have been reported, including low expression alleles and genotype/phenotype correlations that predict severity for certain porphyrias. The tissue-specific regulation of heme biosynthesis and the unique genetic mechanisms for each porphyria are highlighted.

Porphyrias: A 2015 update

The hereditary porphyrias comprise a group of eight metabolic disorders of the heme biosynthesis pathway. Each porphyria is caused by abnormal function at a separate enzymatic step resulting in a specific accumulation of heme precursors. Porphyrias are classified as hepatic or erythropoietic, based on the organ system in which heme precursors (δ-aminolevulinic acid [ALA], porphobilinogen and porphyrins) are overproduced. Clinically, porphyrias are characterized by acute neurovisceral symptoms, skin lesions or both. However, most if not all the porphyrias impair hepatic or gastrointestinal function. Acute hepatic porphyrias present with severe abdominal pain, nausea, constipation, confusion and seizure, which may be life threatening, and patients are at risk of hepatocellular carcinoma without cirrhosis. Porphyria Cutanea presents with skin fragility and blisters, and patients are at risk of hepatocellular carcinoma with liver iron overload. Erythropoietic protoporphyria and X-linked protoporphyria present with acute painful photosensitivity, and patients are at risk of acute liver failure. Altogether, porphyrias are still underdiagnosed, but once they are suspected, early diagnosis based on measurement of biochemical metabolites that accumulate in the blood, urine, or feces is essential so specific treatment can be started as soon as possible and long-term liver complications are prevented. Screening families to identify presymptomatic carriers is also crucial to prevent overt disease and chronic hepatic complications.

[The laboratory diagnostics of disorders of porphyrin metabolism: a lecture]

The lecture presents data concerning biosynthesis of haem and mechanisms of its regulation in bone marrow and liver. The basic pathogenic mechanisms of porphyrias development and their classification are exposed. The optimal list of laboratory tests to diagnose porphyrias is presented. The role and significance of various laboratory analysis techniques to diagnose porphyrias are demonstrated. The technology of laboratory analysis in case of porphyria suspicion is described.

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.

[Laboratory tests and therapeutic strategies for the porphyrias]

The porphyrias are a heterogeneous group of predominantly hereditary metabolic diseases resulting from a dysfunction of heme biosynthesis. Most of the porphyrias can manifest with a broad range of cutaneous symptoms on the sun-exposed areas of the body, whereas other variants reveal life-threatening acute neurological attacks. Further, mixed types of porphyrias exist. Besides the skin, other organs can be affected, such as the liver and the central nervous system. Therefore, interdisciplinary supervision of these patients is mandatory. In this review we will first present the clinical picture and diagnosis of the porphyrias, including the specific biochemical laboratory tests and a diagnostic algorithm. Thereafter, the current therapeutic concepts will be briefly addressed. Finally, we introduce the European Porphyria Initiative (EPI), an association of various European porphyria centers that is aiming at gathering the broad experience of internationally renowned porphyria experts for the development of European consensus guidelines for diagnosis and treatment of these metabolic disorders.

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.

The porphyrias: clinical presentation, diagnosis and treatment

The porphyrias comprise a clinically and genetically heterogeneous group of diseases mostly arising from a genetically determined dysfunction of specific enzymes along the pathway of heme biosynthesis. Based on the occurrence or absence of cutaneous symptoms and life-threatening acute neurological attacks, the different types of porphyrias can either be classified into cutaneous and non-cutaneous forms or acute and non-acute forms. Establishing an accurate diagnosis might be difficult for two reasons: i) the porphyrias can manifest with a broad but unspecific spectrum of clinical symptoms mimicking several other disorders, and ii) biochemical examination of urine, feces, and blood can reveal overlapping findings. Fortunately, however, the advances in the fields of molecular genetics during recent years have provided us with the possibility of overcoming these diagnostic pitfalls. Therefore, in controversial cases the correct diagnosis can finally be made using molecular biological techniques. Due to the various facets of the porphyrias, diagnosis and treatment should always imply a close interdisciplinary collaboration to counsel and help patients and their families most efficiently.

The porphyrias

The porphyrias are a group of disorders involving enzymatic defects in heme synthesis. The porphyrias classically manifest neuro-visceral or photocutaneous symptoms based on which enzyme in the heme metabolic pathway is deficient. Although rare, the porphyrias would most likely be encountered in the emergency department in patients presenting with chronic unspecified abdominal or musculoskeletal pain and those with new onset of psychiatric complaints.

Neurovisceral porphyrias: what a hematologist needs to know

The acute or inducible hepatic porphyrias comprise four inherited disorders of heme biosynthesis. They usually remain asymptomatic for most of the lifespan of individuals who inherit the specific enzyme deficiencies but may cause life-threatening attacks of neurovisceral symptoms. Failure to consider the diagnosis frequently delays effective treatment, and inappropriate diagnostic tests and/or mistaken interpretation of results may lead to misdiagnosis and inappropriate treatment. The four disorders are ALA dehydratase deficiency porphyria, acute intermittent porphyria, hereditary coproporphyria, and variegate porphyria. Other conditions that clinically and biochemically may mimic acute porphyria include lead poisoning and hereditary tyrosinemia type I. The diagnosis of one of these acute porphyric syndromes should be considered in many patients with otherwise unexplained abdominal pain, severe constipation, systemic arterial hypertension, or other characteristic symptoms. Critical to the rapid diagnosis of the three most common of these disorders is demonstration of markedly increased urinary porphobilinogen (PBG) in a single-void urine specimen. The treatment of choice for all but mild attacks of the acute porphyrias is intravenous hemin therapy, which should be started as soon as possible. Intravenous glucose alone is recommended only for mild attacks (no weakness or hyponatremia) or until hemin is available.

Discovery of a group I intron in the SSU rDNA of Ploeotia costata (Euglenozoa)

The gene coding for the small ribosomal subunit RNA of Ploeotia costata contains an actively splicing group I intron (Pco.S516) which is unique among euglenozoans. Secondary structure predictions indicate that paired segments P1-P10 as well as several conserved elements typical of group I introns and of subclass IC1 in particular are present. Phylogenetic analyses of SSU rDNA sequences demonstrate a well-supported placement of Ploeotia costata within the Euglenozoa; whereas, analyses of intron data sets uncover a close phylogenetic relation of Pco.S516 to S-516 introns from Acanthamoeba, Aureoumbra lagunensis (Stramenopila) and red algae of the order Bangiales. Discrepancies between SSU rDNA and intron phylogenies suggest horizontal spread of the group I intron. Monophyly of IC1 516 introns from Ploeotia costata, A. lagunensis and rhodophytes is supported by a unique secondary structure element: helix P5b possesses an insertion of 19 nt length with a highly conserved tetraloop which is supposed to take part in tertiary interactions. Neither functional nor degenerated ORFs coding for homing endonucleases can be identified in Pco.S516. Nevertheless, degenerated ORFs with His-Cys box motifs in closely related intron sequences indicate that homing may have occurred during evolution of the investigated intron group.

The management of porphyria in dental practice

From time to time a patient may attend your practice with a systemic condition that you may or may not remember from the small print of your undergraduate text books. This paper describes one such systemic condition, porphyria, and its dental management. This paper also describes the use of relative analgesia as an aid to anxiety management in porphyria.

Nonsteroidal antiinflammatory drug-induced pseudoporphyria: a case series

BACKGROUND

Pseudoporphyria is a diagnosis that is used when porphyria-like clinical lesions arise in the setting of normal porphyrin levels. This condition was first described in the 1960s and was initially related to the use of certain antibiotic drugs. In 1985, pseudoporphyria was first attributed to the use of nonsteroidal antiinflammatory drugs (NSAIDs). Subsequently, a host of NSAIDs and other drugs have been found to elicit the same clinical entity. The exact mechanism by which certain drugs create clinical lesions resembling porphyria cutanea tarda or erythropoietic protoporphyria is still unknown. A phototoxic mechanism is hypothesized.

OBJECTIVE

We describe six patients diagnosed with pseudoporphyria and detail the diagnostic tests leading to the eventual diagnosis.

RESULTS

The patients ranged in age from 27 to 59 years and had a female:male predominance of 2:1. The offending NSAID was DayPro (oxaprozin) for three of the patients, Relafen (nabumetone) for two of the patients, and Aleve (naproxen) for one patient. For each patient, histology and immunofluorescence was either consistent with the diagnosis of porphyria cutanea tarda or nonspecific, while serum, stool, and urine porphyrins did not support that diagnosis. Withdrawal of the offending agent provided relief from the clinical symptoms for each patient. None of our patients were rechallenged with the putative offending drug. However, prolonged avoidance has provided a sustained remission from symptoms in all six patients.

CONCLUSIONS

Pseudoporphyria is a relatively rarely reported condition. Clinical suspicion with appropriate laboratory and histopathologic findings help to make this diagnosis, and exclude true porphyrias. Rechallenge with the offending drug to produce symptom relapse has been proposed to be helpful in confirming this diagnosis of exclusion. Since all 6 patients with drug-induced pseudoporphyria experienced resolution of their symptoms after discontinuing the offending agent, we propose that this clinical correlation alone is sufficient to confirm this diagnosis. Our observation of six new cases of NSAID-induced pseudoporphyria over a two-year interval suggests that this is not a rare entity.

[Nephrologists and porphyrias]

As usually occurs for rare diseases, the word "PORPHYRIA" often recalls a confused topic with shaded boundaries, presenting "bullous" skin lesions, rare opportunity of diagnosis in clinical practice, unknown pathogenesis, and almost absent therapeutic options. The goal of this review is to draw attention to this topic, as new diagnostic and therapeutic tools might change the natural history of this disease. Porphyrias are disorders resulting from abnormalities of porphyrin metabolism. Porphyrins are molecules made up of four pyrrol rings, which constitute haeme-proteins, including haemoglobin. Following the "trigger" enzyme delta-aminolevulinic acid (ALA) synthase, which is capable of condensing succynil CoA and glycine, seven additional enzymes are involved in the process that eventually leads to haeme biosynthesis. Porphyrias are the result of total or partial deficiencies in these seven enzymes involved in haeme synthesis. Usually, the final haeme product exerts a negative feed-back on its synthesis. The enzyme deficiency that occurs in porphyrias is responsible for reduced haeme production, which, in turn, allows the cascade to be stimulated by increased activity of the trigger enzyme, ALA-synthase (ALA-s). However, due to the subsequent enzyme defects, notwithstanding increased ALA-s activity, haeme synthesis is blunted and intermediate metabolites accumulate. Clinical manifestations depend on which step the enzymatic defect occurs: if enzymatic defects are in the initial steps of the metabolic cascade, early metabolic intermediates will accumulate [i.e. ALA and porphobilinogen (PBG)] responsible for attacks of neurological dysfunction; if the enzymatic defects are in the final steps, sunlight-induced cutaneous lesions (phtotosensitivity) due to porphyrin accumulation in the skin will develop. The seven major human porphyrias may be classified into "hepatic or erythropoietic porphyrias" depending on the organ/tissue where metabolic alterations are more evident, or "acute or chronic porphyrias" depending on the prevalence of clinical symptoms, if neurologic (acute) or cutaneous (chronic). Only a small number of people with inherited enzyme deficiency will develop overt clinical disease, mainly because of the role of acquired aggravating and precipitating factors, such as drugs, hormonal causes, infection, caloric restriction, alcohol. The biochemical diagnosis of porphyrias relies on the detection of the consequences of increased ALA-s activity in the liver: overproduction, accumulation and increased excretion of early (ALA, PBG) or late (porphyrins) intermediate compounds in plasma, faeces and urine. A major difficulty arises from the knowledge that such abnormalities may be completely absent during the remission phases of the disease. Only in very specialised Centres it is now possible to measure specific haeme synthesis enzyme defects, and to perform molecular diagnosis by DNA analysis. The true prevalence of the diseases is unknown, ranging from 1:500 to 1:50,000. Therapeutic strategies include withdrawal of all common precipitants (drug, alcohol, fasting, infection), use of opiates and chlorpromazine, carbohydrates (300-400 g/day) and infusion of human haemine. Genetic therapies are being studied for the future.

[Laboratory approximation to the diagnosis and typification of porphyria]

The relationship between clinical features and specific alterations of heme metabolism allows the accurate diagnosis and classification of porphyrias. The acute porphyric attack is characterized by frequently confusing clinical pattern of abdominal-psiquic- and neurological symptoms. An increased urinary excretion of porphobilinogen, which can be quickly detected by the Hoesch test, confirms the diagnosis of this acute attack. Increased plasma porphyrin levels are associated with skin lesions, which are the characteristic features of the cutaneous porphyrias. Their presence is easily and rapidly detected by a fluorimetric scanning of PBS (phosphate buffer saline) diluted samples. Characterization of the molecular defects in genes coding for the enzymes involved in the heme synthetic pathway is complementary to the biochemical methods. Molecular analysis permits an accurate classification of those biochemically unclassified patients and allows prenatal diagnosis in those homozygotic cases where a severe prognosis is suspected.

Acute porphyric disorders

Acute porphyrias are classified into 3 distinct groups of rare genetic disorders of metabolic enzyme biosynthesis. Acute porphyrias can significantly impact multiple organ systems, which often provides a challenge to the dentist presented with such a patient. A case of hereditary coproporphyria is reported in a patient with many of the classical signs and symptoms. The patient also had complex dental needs that required special medical and pharmacotherapeutic modifications. The acute porphyrias are reviewed by the authors with presentation of this challenging case. Recommendations for other dental health care professionals encountering these patients are then presented.

Lipoprotein abnormalities in patients with asymptomatic acute porphyria

There have been discrepancies in reports of total cholesterol and low density lipoprotein (LDL)-cholesterol levels in patients with acute porphyria. Some studies have found that acute porphyria patients have increased levels while others do not. The aim of this study has been to evaluate the lipid profile in a series of patients with acute porphyria, in order to help clarify these differences. Serum lipoprotein levels were studied in 30 patients (25 women and five men; age:38+/-10 years) with asymptomatic acute porphyria. Controls were 30 healthy volunteers matched for age and gender. For 13 patients and 15 controls, lipoprotein lipase and hepatic lipase activities were determined. Patients exhibited increased levels of total-cholesterol, LDL-cholesterol, high density lipoprotein (HDL)-cholesterol and apolipoprotein (apo)-A1 compared with controls (P4 mmol/l in 15 patients (50%). Levels of total triglycerides, very low density lipoprotein (VLDL)-triglycerides, VLDL-cholesterol, apo-B and lipoprotein(a) were similar in patients and controls. The hepatic lipase activity tended to be lower in patients than controls (33.8+/-17.7 vs. 50.4+/-23.0 pkat/ml; P=0.05). In conclusion, in patients with asymptomatic acute porphyria an increase of total and LDL-cholesterol was found. The cardiovascular risk conferred by this factor may be attenuated by increased HDL-cholesterol and apo-A1.

Alcohol and porphyrin metabolism

Alcohol is a porphyrinogenic agent which may cause disturbances in porphyrin metabolism in healthy persons as well as biochemical and clinical manifestations of acute and chronic hepatic porphyrias. After excessive consumption of alcohol, a temporary, clinically asymptomatic secondary hepatic coproporphyrinuria is observable, which can become persistent in cases of alcohol-induced liver damage. Nowadays, the alcohol-liver-porphyrinuria syndrome is the first to be mentioned in secondary hepatic disturbances of porphyrin metabolism. Acute hepatic porphyrias (acute intermittent porphyria, variegate porphyria and hereditary coproporphyria) are considered to be molecular regulatory diseases, in contrast to non-acute, chronic hepatic porphyria, clinically appearing as porphyria cutanea tarda (PCT). Porphyrins do not accumulate in the liver in acute porphyrias, whereas in chronic hepatic porphyrias they do. Thus, chronic hepatic porphyria is a porphyrin-accumulation disease, whereas acute hepatic porphyrias are haem-pathway-dysregulation diseases, characterized in general by induction of delta-aminolevulinic acid synthase in the liver and excessive stimulation of the pathway without storage of porphyrins in the liver. The clinical expression of acute hepatic porphyrias can be triggered by alcohol, because alcohol augments the inducibility of delta-aminolevulinic acid synthase. In chronic hepatic porphyrias, however, which are already associated with liver damage, alcohol potentiates the disturbance of the decarboxylation of uro- and heptacarboxyporphyrinogen, which is followed by a hepatic accumulation of uro- and heptacarboxyporphyrin and their sometimes extreme urinary excretion. Especially in persons with a genetic deficiency of uroporphyrinogen decarboxylase, but also in patients with the so-called sporadic variety of PCT, alcohol is able to transform an asymptomatic coproporphyrinuria into PCT. Alcohol has many biochemical and clinical effects on porphyrin and haem synthesis both in humans and laboratory animals. Ethanol suppresses the activity of porphobilinogen synthase (synonym: delta-aminolevulinic acid dehydratase), uroporphyrinogen decarboxylase, coproporphyrinogen oxidase and ferrochelatase, whereas it induces the first and rate-limiting enzyme in the pathway, delta-aminolevulinic acid synthase and also porphobilinogen deaminase. Therefore, teetotalism is a therapeutically and prophylactically important measure in all types of hepatic porphyrias.

Biochemical differentiation of the porphyrias

OBJECTIVES

To differentiate the porphyrias by clinical and biochemical methods.

DESIGN AND METHODS

We describe levels of blood, urine, and fecal porphyrins and their precursors in the porphyrias and present an algorithm for their biochemical differentiation. Diagnoses were established using clinical and biochemical data. Porphyrin analyses were performed by high performance liquid chromatography.

RESULTS AND CONCLUSIONS

Plasma and urine porphyrin patterns were useful for diagnosis of porphyria cutanea tarda, but not the acute porphyrias. Erythropoietic protoporphyria was confirmed by erythrocyte protoporphyrin assay and erythrocyte fluorescence. Acute intermittent porphyria was diagnosed by increases in urine delta-aminolevulinic acid and porphobilinogen and confirmed by reduced erythrocyte porphobilinogen deaminase activity and normal or near-normal stool porphyrins. Variegate porphyria and hereditary coproporphyria were diagnosed by their characteristic stool porphyrin patterns. This appears to be the most convenient diagnostic approach until molecular abnormalities become more extensively defined and more widely available.

Porphyria and its investigation

The porphyrias are inherited disorders of haem synthesis and must be considered in the differential diagnosis of numerous disorders.

Anaesthesia for porphyria

Porphyrias arise due to enzyme defects in the haem synthetic pathway. They are of concern to the anaesthetist as acute crises may be precipitated by anaesthetic drugs. Anaesthesia must be carefully managed in patients with porphyria in order to achieve a successful outcome.

Porphyrin enzyme analysis in an oral pathology practice: a look back over four years

The porphyrias are defined by specific enzymes having diminished activity. More enzymes have become available for routine testing. Measurement of urine and stool porphyrin and porphyrin precursor elevations are important, but in many instances are not found or found in confusing patterns. The use of enzyme analysis can often be helpful in identifying those patients with a genetically diminished enzyme activity level. Looking back over the last four years, modifications in evaluating patients for porphyria were developed and are related in this article. In 91 patients, patterns of enzyme deficiencies were seen that have been observed by others; however, new observations have been made. While many of the enzymes in the porphyrin pathway are available for testing, others need to come on line as soon as possible, particularly protoporphyrinogen oxidase.

[The porphyrias: it's definition, classification and differential diagnosis]

The porphyrias are diseases of enzyme deficiency in the heme synthetic pathway. They are classified into eight subtypes, two of which, ALADP and HEP, have been added as new subtypes during the past 10 years. These eight subtypes are divided into two groups, hepatic and erythropoietic. Hepatic porphyrias include AIP, ALADP, VP, HCP, PCT and HEP. Erythropoietic porphyrias consist of two subtypes, CP and EPP. From the clinical point of view, these subtypes may, also, be divided into acute and cutaneous porphyrias. AIP, ALADP, VP and HCP belong to acute porphyria. CP, EPP, PCT, and HEP to cutaneous porphyria. The diagnosis of porphyrias and differential diagnosis of subtypes are made by analyzing porphyrias and it's precursors in urine, blood and feces.

[A study of an automated porphyria diagnosis system using urinary porphyrin profile analysis]

Porphyrins are essential substances for the biosynthesis of heme. Porphyria results from a disorder in the metabolism of porphyrin. Patients suffering from Porphyria exhibit changes in their porphyrin profiles as measured in excretia and organs. A highly sensitive and simple analytical method using high-performance liquid chromatography (HPLC) for all porphyrin metabolites in urine was established. This method is able to separate porphyrins such as uroporphyrin, carboxylic acid porphyrins of hepta-, hexa-, penta-, and coproporphyrin isomers of I and III in a sample of human urine. In this study, the combination of HPLC with a computer system for automated porphyria diagnosis was investigated. The profile of all urinary porphyrins from patients with various Porphyria were measured by HPLC and diagnosed by the computer diagnostic system. This system enabled the estimation of 5 types of porphyrias with a high accuracy of diagnosis.

[Porphyrias and drugs]

The porphyrias are a metabolic disorders of heme biosynthesis characterized by the excessive production and excretion of porphyrins and porphyrin precursors. They are caused by defects in specific enzyme activities and classified into 7 subtypes. Some of them present with photosensitivity of skin and intermittent acute attacks related to nervous system disturbance. Especially in acute intermittent porphyria, patients have recurrent acute attacks of abdominal, neurologic, and psychiatric symptoms. Some precipitating factors; including drugs, hormonal factors, starvation, and stress; induces acute attacks. In this article, pathophysiology of the neurologic symptoms and relation between precipitating factors, especially focused in drugs, and acute attacks may be reviewed.

[Treatment of the porphyrias]

There are seven porphyrias which are caused by defective functions of the enzymes in the haem biosynthesis. The clinical classification of porphyrias are divided into three types which are neuroporphyria, neurocutaneous porphyria and cutaneous porphyria. For acute porphyric attack of neuroporphyria and neurocutaneous porphyria, the treatments of choice are administration of glucose and/or hematin, haem arginate and tinprotoporphyrin. Porphyria cutanea tarda in cutaneous porphyria is controlled by removal of iron by phrebotomies or low-dose chloriquine. A novel approach of intravenous administration of interferon may be useful to control the associated case of chronic hepatitis type C. Skin symptoms in erythropoietic protoporphyria can be alleviated with beta carotene. Hepatic failure due to protoporphyria may need a liver transplantation. Cimetidine, a H2-receptor antagonist, may be useful in the treatment of acute porphyric attack and in remission stage in neuroporphyrias, neurocutaneous porphyrias and cutaneous porphyrias such as porphyria cutanea tarda and protoporphyria.

Porphyria: reexamination of psychiatric implications

Acute intermittent porphyria mimics a variety of commonly occurring disorders and thus poses a diagnostic quagmire. Psychiatric manifestations include hysteria, anxiety, depression, phobias, psychosis, organic disorders, agitation, delirium, and altered consciousness ranging from somnolence to coma. Some patients develop psychosis similar to schizophrenia. Psychiatric hospitals have a disproportionate number of patients with this disorder as only difficult and resistant patients accumulate there. Presence of photosensitive porphyrins in the urine is diagnostic. When porphyrins are absent, excess of alpha aminolevulinic acid and porphobilinogen are present in the urine. The definitive test is to measure monopyrrole porphobilinogen deaminase in RBCs. This diagnosis should be entertained in the following situations: (a) unexplained leukocytosis; (b) unexplained neuropathy; (c) etiologically obscure neurosis or psychosis; (d) 'idiopathic' seizure disorder; (e) unexplained abdominal pain; (f) conversion hysteria, and (g) susceptibility to stress. Porphyria is important in psychiatry as it may present with only psychiatric symptoms; it may masquerade as a psychosis and the patient may be treated as a schizophrenic person for years; the only manifestation may be histrionic personality disorder which may not receive much attention. Diagnosis is based on a high index of suspicion and appropriate investigation. Various psychotropic drugs exacerbate acute attacks. While it is important not to use the unsafe drugs in porphyric patients, it is also imperative to look for this diagnosis in cases where these drugs produce unprecedented drug reactions.

Acute porphyrias: diagnosis and management

To summarize recent information about acute porphyrias and to provide clinicians with a practical diagnostic and management approach, we reviewed the pertinent literature and our clinical experience. The acute porphyrias are characterized by recurrent attacks of abdominal pain with or without additional manifestations of autonomic dysfunction or neuropsychiatric symptoms. On the basis of the potential of these disorders to affect the skin, they are further subdivided into neuroporphyrias and neurocutaneous porphyrias. During acute attacks, acute porphyria is always associated with increased levels of urinary porphyrin precursors. Between attacks, patients with neurocutaneous porphyrias may have normal urinary porphyrins; therefore, stool porphyrins, which are invariably increased, are the most helpful. Latent disease can be detected by the measurement of either urinary and stool porphyrins or cellular enzyme activity. Specific intravenous therapy with hematin has resulted in biochemical remissions, but its clinical benefit remains controversial. Measurement of urinary and stool porphyrins or porphyrin precursors is critical for the diagnosis of clinically overt acute porphyria. Enzyme assays are helpful in supporting the diagnosis but are best used to identify family members with latent disease. Preventive measures and supportive therapy are the mainstays of current management of patients with porphyria.

Composition of urinary coproporphyrin isomers I-IV in human porphyrias

The urinary distribution and relative proportions of the four coproporphyrin isomers I-IV were investigated in 50 patients suffering from hepatic and erythropoietic types of hereditary porphyrias. A highly efficient sample preparation method was applied to isolate urinary coproporphyrins, the isomer ratios of which were quantitated by isocratic ion-pair high-performance liquid chromatography. Results showed a significant decrease (p < 0.001) of the proportion of coproporphyrin I in acute hepatic porphyria (acute intermittent porphyria, hereditary coproporphyria, variegate porphyria, porphobilinogen synthase deficiency porphyria) as compared with chronic hepatic porphyria (porphyria cutanea tarda, chronic hepatic porphyria type B and C) (13.2 +/- 5.3%, mean +/- S.D., vs. 31.4 +/- 11.5%). Conversely, the proportion of isomer III was significantly higher (p < 0.001) in acute hepatic porphyria than in chronic hepatic porphyria (80.9 +/- 5.2% vs. 62.2 +/- 10.9%). As expected, the highest level of coproporphyrin I (90.0 +/- 1.9%) was found in congenital erythropoietic porphyria. The atypical coproporphyrins II and IV were detected in all types of porphyria analysed and ranged from 0.2 to 9.0%; no significant differences were seen between acute and chronic hepatic porphyrias. The diagnostic importance of the isomer ratios of coproporphyrins I and III has been confirmed in our study, while the significance of the atypical coproporphyrin isomers II and IV is still unclear at present.

[Alcoholic liver damage and impaired porphyrin metabolism]

The authors review the alcohol-induced acquired defect of the porphyrin metabolism. They think that the free radicals formed during the alcohol metabolism may have an important role in the producing of the enzyme defects and in the accomplishment of the acute attack in the genetic porphyrias. In the first part of the article they summarize the genetic hepatic porphyrias, main symptoms, the therapy and the mechanism of the free radical forming during the alcohol metabolism.

Clinical utility of fluorometric scanning of plasma porphyrins for the diagnosis and typing of porphyrias

The fluorometric emission scanning (using excitation at 405 nm) of plasma samples, simply diluted five-fold in phosphate-buffered saline, allows the differentiation of three conditions according to their porphyrin content. The emission maximum at 626-628 nm is a specific finding in variegate porphyria, while in erythropoietic protoporphyria a characteristic peak is found at 636 nm. A fluorescence emission maximum at 618-622 nm corresponds to a third group that includes normal subjects, non-porphyria patients and patients suffering from acute intermittent porphyria, hereditary coproporphyria, congenital erythropoietic porphyria (Günther disease) and porphyria cutanea tarda. Therefore, this simple, quick and cheap screening test allows one to establish whether a patient with a photocutaneous syndrome has porphyria and whether this porphyria belongs to the types: variegate, protoporphyria or other cutaneous porphyrias.