Porphyrias

Adrenal hormonal imbalance in acute intermittent porphyria patients: results of a case control study

Background

Acute Intermittent Porphyria (AIP) is a rare disease that results from a deficiency of hydroxymethylbilane synthase, the third enzyme of the heme biosynthetic pathway. AIP carriers are at risk of presenting acute life-threatening neurovisceral attacks. The disease induces overproduction of heme precursors in the liver and long-lasting deregulation of metabolic networks. The clinical history of AIP suggests a strong endocrine influence, being neurovisceral attacks more common in women than in men and very rare before puberty. To asses the hypothesis that steroidogenesis may be modified in AIP patients with biochemically active disease, we undertook a comprehensive analysis of the urinary steroid metabolome.

Methods

A case–control study was performed by collecting spot morning urine from 24 AIP patients and 24 healthy controls. Steroids in urine were quantified by liquid chromatography-tandem mass spectrometry. Parent steroids (17-hydroxyprogesterone; deoxycorticosterone; corticoesterone; 11-dehydrocorticosterone; cortisol and cortisone) and a large number of metabolites (N = 55) were investigated. Correlations between the different steroids analyzed and biomarkers of porphyria biochemical status (urinary heme precursors) were also evaluated. The Mann–Whitney U test and Spearman’s correlation with a two tailed test were used for statistical analyses.

Results

Forty-one steroids were found to be decreased in the urine of AIP patients (P < 0.05), the decrease being more significant for steroids with a high degree of hydroxylation. Remarkably, 13 cortisol metabolites presented lower concentrations among AIP patients (P < 0.01) whereas no significant differences were found in the main metabolites of cortisol precursors. Nine cortisol metabolites showed a significant negative correlation with heme precursors (p < 0.05). Ratios between the main metabolites of 17-hydroxyprogesterone and cortisol showed positive correlations with heme-precursors (correlation coefficient > 0.51, P < 0.01).

Conclusions

Comprehensive study of the urinary steroid metabolome showed that AIP patients present an imbalance in adrenal steroidogenesis, affecting the biosynthesis of cortisol and resulting in decreased out-put of cortisol and metabolites. This may result from alterations of central origin and/or may originate in specific decreased enzymatic activity in the adrenal gland. An imbalance in steroidogenesis may be related to the maintenance of an active disease state among AIP patients.

Antisense oligonucleotide-based therapy in human erythropoietic protoporphyria

In 90% of people with erythropoietic protoporphyria (EPP), the disease results from the inheritance of a common hypomorphic FECH allele, encoding ferrochelatase, in trans to a private deleterious FECH mutation. The activity of the resulting FECH enzyme falls below the critical threshold of 35%, leading to the accumulation of free protoporphyrin IX (PPIX) in bone marrow erythroblasts and in red cells. The mechanism of low expression involves a biallelic polymorphism (c.315-48T>C) localized in intron 3. The 315-48C allele increases usage of the 3' cryptic splice site between exons 3 and 4, resulting in the transcription of an unstable mRNA with a premature stop codon, reducing the abundance of wild-type FECH mRNA, and finally reducing FECH activity. Through a candidate-sequence approach and an antisense-oligonucleotide-tiling method, we identified a sequence that, when targeted by an antisense oligonucleotide (ASO-V1), prevented usage of the cryptic splice site. In lymphoblastoid cell lines derived from symptomatic EPP subjects, transfection of ASO-V1 reduced the usage of the cryptic splice site and efficiently redirected the splicing of intron 3 toward the physiological acceptor site, thereby increasing the amount of functional FECH mRNA. Moreover, the administration of ASO-V1 into developing human erythroblasts from an overtly EPP subject markedly increased the production of WT FECH mRNA and reduced the accumulation of PPIX to a level similar to that measured in asymptomatic EPP subjects. Thus, EPP is a paradigmatic Mendelian disease in which the in vivo correction of a common single splicing defect would improve the condition of most affected individuals.

Heme acts through the Bach1b/Nrf2a-MafK pathway to regulate exocrine peptidase precursor genes in porphyric zebrafish

Using a zebrafish model of hepatoerythropoietic porphyria (HEP), we identify a previously unknown mechanism underlying heme-mediated regulation of exocrine zymogens. Zebrafish bach1b, nrf2a and mafK are all expressed in the zebrafish exocrine pancreas. Overexpression of bach1b or knockdown of nrf2a result in the downregulation of the expression of the exocrine zymogens, whereas overexpression of nrf2a or knockdown of bach1b cause their upregulation. In vitro luciferase assays demonstrate that heme activates the zymogens in a dosage-dependent manner and that the zymogen promoter activities require the integral Maf recognition element (MARE) motif. The Bach1b-MafK heterodimer represses the zymogen promoters, whereas the Nrf2a-MafK heterodimer activates them. Furthermore, chromatin immunoprecipitation (ChIP) assays show that MafK binds to the MARE sites in the 5' regulatory regions of the zymogens. Taken together, these data indicate that heme stimulates the exchange of Bach1b for Nrf2a at MafK-occupied MARE sites and that, particularly in heme-deficient porphyria, the repressive Bach1b-MafK heterodimer dominates, which can be exchanged for the activating Nrf2a-MafK heterodimer upon treatment with hemin. These results provide novel insights into the regulation of exocrine function, as well as the pathogenesis of porphyria, and should be useful for designing new therapies for both types of disease.

Clinical and forensic signs related to ethanol abuse: a mechanistic approach

For good performance in clinical and forensic toxicology, it is important to be aware of the signs and symptoms related to xenobiotic exposure since they will assist clinicians to reach a useful and rapid diagnosis. This manuscript highlights and critically analyses clinical and forensic imaging related to ethanol abuse. Here, signs that may lead to suspected ethanol abuse, but that are not necessarily related to liver disease are thoroughly discussed regarding its underlying mechanisms. This includes flushing and disulfiram reactions, urticaria, palmar erythema, spider telangiectasias, porphyria cutanea tarda, "paper money skin", psoriasis, rhinophyma, Dupuytren's contracture, multiple symmetrical lipomatosis (lipomatosis Lanois-Bensaude, Madelung's disease), pancreatitis-related signs, black hairy tongue, gout, nail changes, fetal alcohol syndrome, seborrheic dermatitis, sialosis and cancer.

Erythropoietic protoporhyria in first pregnancy

Erythropoietic protoporphyria is a rare, inherited disorder, mainly characterised by photosensitivity. Its accompanying vitamin D and iron deficiencies, as well as potential effects on the liver, make it an important condition to monitor in pregnancy. However, as discovered in our subject case, pregnancy and delivery appear to pose little additional burden to the woman or baby, and in fact, may lead to an improvement of symptoms.

Separation and fragmentation study of isocoproporphyrin derivatives by UHPLC-ESI-exact mass MS/MS and identification of a new isocoproporphyrin sulfonic acid metabolite

Isocoproporphyrin and its derivatives are commonly used as biomarkers of porphyria cutanea tarda, heavy metal toxicity and hexachlorobenzene (HCB) intoxication in humans and animals. However, most are isobaric with other porphyrins and reference materials are unavailable commercially. The structural characterisation of these porphyrins is important but very little data is available. We report here the separation and characterisation of isocoproporphyrin, deethylisocoproporphyrin, hydroxyisocoproporphyrin and ketoisocoproporphyrin, isolated in the faeces of rats fed with a diet containing HCB, by ultra high performance liquid chromatography-exact mass tandem mass spectrometry (UHPLC-MS/MS). Furthermore, we report the identification and characterisation of a previously unreported porphyrin metabolite, isocoproporphyrin sulfonic acid isolated in the rat faeces. The measured mass-to-charge ratio (m/z) of the precursor ion was m/z 735.2338, corresponding to a molecular formula of C36H39N4O11S with an error of 0.3 ppm from the calculated m/z 735.2336. The MS/MS data was consistent with an isocoproporphyrin sulfonic acid structure, derived from dehydroisocoproporphyrinogen by sulfonation of the vinyl group. The metabolite was present in a greater abundance than other isocoproporphyrin derivatives and may be a more useful biomarker for HCB intoxication.

Was the death of Alexander the Great due to poisoning? Was it Veratrum album?

OBJECTIVE

To investigate the death of Alexander the Great to determine if he died from natural causes or was poisoned and, if the latter, what was the most likely poison.

METHODS

OVID MEDLINE (January 1950-May 2013) and ISI Web of Science (1900-May 2013) databases were searched and bibliographies of identified articles were screened for additional relevant studies. These searches identified 53 relevant citations. Classical literature associated with Alexander's death. There are two divergent accounts of Alexander's death. The first has its origins in the Royal Diary, allegedly kept in Alexander's court. The second account survives in various versions of the Alexander Romance. Nature of the terminal illness. The Royal Diary describes a gradual onset of fever, with a progressive inability to walk, leading to Alexander's death, without offering a cause of his demise. In contrast, the Romance implies that members of Alexander's inner circle conspired to poison him. The various medical hypotheses include cumulative debilitation from his previous wounds, the complications of alcohol imbibing (resulting in alcohol hepatitis, acute pancreatitis, or perforated peptic ulcer), grief, a congenital abnormality, and an unhealthy environment in Babylon possibly exacerbated by malaria, typhoid fever, or some other parasitic or viral illness. Was it poisoning? Of all the chemical and botanical poisons reviewed, we believe the alkaloids present in the various Veratrum species, notably Veratrum album, were capable of killing Alexander with comparable symptoms to those Alexander reportedly experienced over the 12 days of his illness. Veratrum poisoning is heralded by the sudden onset of epigastric and substernal pain, which may also be accompanied by nausea and vomiting, followed by bradycardia and hypotension with severe muscular weakness. Alexander suffered similar features for the duration of his illness.

CONCLUSION

If Alexander the Great was poisoned, Veratrum album offers a more plausible cause than arsenic, strychnine, and other botanical poisons.

Neuropathic pain in hereditary coproporphyria

Acute porphyrias are rare diseases with varying incidences worldwide. These diseases are disorders of heme biosynthesis characterized by acute attacks of neurological symptoms. Acute porphyria should be considered in patients with unexplained abdominal pain or neurological damage. Clinical manifestations of acute porphyria are nonspecific and are associated with multiple organ systems. This report examines a rare case of an uncommon type of acute porphyria in a patient with an initial presentation of abdominal pain and progressive polyneuropathy.

Kidney transplantation in hereditary coproporphyria using tacrolimus and mycophenolate mofetil: a case report

BACKGROUND

The porphyrias are a group of disorders of the heme biosynthesis pathway that may present with acute life-threatening attacks, commonly exacerbated by a wide variety of medications. Many newer immunosuppressive medications, which are in use following kidney transplantation, have not been fully explored in acute porphyrias.

CASE REPORT

A 53-year-old woman received a kidney from a deceased donor, after being on hemodialysis for 4 years. Hereditary coproporphyria was diagnosed at age 19 years. We administered tacrolimus, mycophenolate mofetil and steroid immunosuppression. In the immediate post-transplant periods she displayed abdominal pain and transient uroporphyrin elevation in parallel with slightly elevated (15 ng/mL) tacrolimus concentrations. As the target tacrolimus level was achieved, these findings disappeared.

CONCLUSIONS

Tacrolimus, mycophenolate- mofetil, and steroid therapy for hereditery coproporphyri was safe, in the long term.

Zebrafish models of human liver development and disease

The liver performs a large number of essential synthetic and regulatory functions that are acquired during fetal development and persist throughout life. Their disruption underlies a diverse group of heritable and acquired diseases that affect both pediatric and adult patients. Although experimental analyses used to study liver development and disease are typically performed in cell culture models or rodents, the zebrafish is increasingly used to complement discoveries made in these systems. Forward and reverse genetic analyses over the past two decades have shown that the molecular program for liver development is largely conserved between zebrafish and mammals, and that the zebrafish can be used to model heritable human liver disorders. Recent work has demonstrated that zebrafish can also be used to study the mechanistic basis of acquired liver diseases. Here, we provide a comprehensive summary of how the zebrafish has contributed to our understanding of human liver development and disease.

Best practice guidelines on clinical management of acute attacks of porphyria and their complications

The British and Irish Porphyria Network guidelines describe best practice in the clinical assessment, investigation and management of acute porphyria attacks and their complications, including severe attacks with neuropathy. Acute attacks of porphyria may occur in acute intermittent porphyria (AIP), variegate porphyria (VP) and hereditary coproporphyria (HCP). Aminolaevulinic acid dehydratase deficiency porphyria (ADP) is a very rare autosomal recessive porphyria; only six cases substantiated by mutation analysis have yet been described in the literature. Urinary porphobilinogen (PBG) is always raised in an acute attack due to AIP, VP or HCP and this analysis is essential to confirm the diagnosis. A positive result in a qualitative or semi-quantitative screening test must be followed by PBG quantitation at the earliest opportunity. However in a severely ill patient, treatment should not be delayed. Removal of precipitating factors, effective analgesia and control of symptoms with safe medication, attention to nutrition and fluid balance are essential. The indications for use of intravenous haem arginate are set out, together with advice on its administration. A small proportion of acute porphyria patients develop recurrent attacks and management options that may be considered include gonadotrophin-releasing hormone analogues, 'prophylactic' regular haem arginate infusion or ultimately, liver transplantation.

Role of genetic testing in the management of patients with inherited porphyria and their families

The porphyrias are a group of mainly inherited metabolic conditions that result from partial deficiency of individual enzymes in the haem biosynthesis pathway. Clinical presentation is either with acute neurovisceral attacks, skin photosensitivity or both, and is due to overproduction of pathway intermediates. The primary diagnosis in the proband is based on biochemical testing of appropriate samples, preferably during or soon after onset of symptoms. The role of genetic testing in the autosomal dominant acute porphyrias (acute intermittent porphyria, hereditary coproporphyria and variegate porphyria) is to identify presymptomatic carriers of the family specific pathogenic mutation so that they can be counselled on how to minimize their risk of suffering an acute attack. At present the additional genetic factors that influence penetrance are not known, and all patients are treated as equally at risk. Genetic testing in the erythropoietic porphyrias (erythropoietic protoporphyria, congenital erythropoietic porphyria and X-linked dominant protoporphyria) is focused on predictive and preconceptual counselling, prenatal testing and genotype-phenotype correlation. Recent advances in analytical technology have resulted in increased sensitivity of mutation detection with success rates of greater than 90% for most of the genes. The ethical and consent issues are discussed. Current research into genetic factors that affect penetrance is likely to lead to a more refined approach to counselling for presymptomatic gene carriers.

Cutaneous porphyrias part II: treatment strategies

The porphyrias are diverse in pathophysiology, clinical presentation, severity, and prognosis, presenting a diagnostic and therapeutic challenge. Although not easily curable, the dermatological manifestations of these diseases, photosensitivity and associated cutaneous pathology, can be effectively prevented and managed. Sun avoidance is essential, and patient education regarding the irreversibility of photocutaneous damage is a necessary corollary. Beyond preventative measures, the care of fragile, vulnerable skin, and pain management, each of the porphyrias has a limited number of unique additional therapeutic options. Many of the treatments have been published only in small case series or anecdotal reports and do not have well-understood nor proven mechanisms of action. This article presents a comprehensive review of available therapeutic options and long-term management recommendations for the cutaneous porphyrias.

Manifestations and treatment of the hand in adult congenital erythropoietic porphyria

Congenital erythropoietic porphyria (CEP) is a rare enzymatic disorder of heme metabolism, leading to the accumulation of porphyrins in the skin and subdermal structures. We present the case of a 34-year-old, right-hand-dominant, male patient with CEP. The patient had developed a chronic open subluxation of the left index finger proximal interphalangeal joint due to skin necrosis. We successfully treated the patient with proximal interphalangeal arthrodesis. This case demonstrates that childhood-onset CEP can also manifest in the adult hand. Considering the patient's age, the destructive nature of the disease, and the poor quality of function in older patients with childhood CEP, surgical intervention was necessary to avoid further digital length loss. Although the treatment described in this case report is not uncommon, we found it essential to present this case because the clinical presentation of CEP is rare.

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.

Update on pediatric photosensitivity disorders

PURPOSE OF REVIEW

Although rare in the pediatric population, photosensitive dermatoses may begin prior to adulthood. The causes of photosensitivity are diverse, ranging from primary, immunologically mediated disorders of photosensitivity to inherited genetic or metabolic disorders. This review will highlight the key features of these disorders to familiarize the pediatric practitioner with their symptoms and any associated extracutaneous clinical or laboratory findings that may accompany them.

RECENT FINDINGS

New developments in the field of pediatric photosensitivity have been scant over recent years. While mechanisms of photosensitivity and genetic underpinnings associated with various conditions such as xeroderma pigmentosum continue to be uncovered, the literature on disorders of photosensitivity has been otherwise without many recent significant advances.

SUMMARY

Although the differential diagnosis of pediatric photosensitivity disorders is broad, it is often possible to establish the diagnosis by following an algorithmic approach. Once the correct diagnosis is rendered, this will guide any further workup that needs to be performed as well as specific management strategies.

Recurrent porphyria attacks in a Chinese patient with a heterozygous PBGD mutation

We report here the case of a 32-year-old Chinese Han woman who presented with frequent severe abdominal pain, convulsion, numbness and confusion. She also had hypertension, hyponatremia, chronic renal failure, anemia and a high urinary δ-aminolevulinic acid concentration. We identified a heterozygous splicing mutation in intron 11 (IVS11-2A→G) of the porphobilinogen (PBG) deaminase gene (PBGD) in her genomic DNA. This mutation had previously been reported in a North American patient, but was absent from 50 healthy Chinese controls.

Photosensitivity in the elderly-think of late-onset protoporphyria

Photosensitivity is the clinical hallmark of both erythropoietic protoporphyria (EPP) and X-linked dominant protoporphyria (XLDPP). Both disorders result from a hereditary dysfunction in heme biosynthesis. Disease onset is usually in early childhood. However, rare patients with late-onset EPP in association with a myeloproliferative disorder or myelodysplastic syndrome have been reported. In this issue, Livideanu et al. describe the first patient with late-onset XLDPP.

The human flavoproteome

Vitamin B2 (riboflavin) is an essential dietary compound used for the enzymatic biosynthesis of FMN and FAD. The human genome contains 90 genes encoding for flavin-dependent proteins, six for riboflavin uptake and transformation into the active coenzymes FMN and FAD as well as two for the reduction to the dihydroflavin form. Flavoproteins utilize either FMN (16%) or FAD (84%) while five human flavoenzymes have a requirement for both FMN and FAD. The majority of flavin-dependent enzymes catalyze oxidation-reduction processes in primary metabolic pathways such as the citric acid cycle, β-oxidation and degradation of amino acids. Ten flavoproteins occur as isozymes and assume special functions in the human organism. Two thirds of flavin-dependent proteins are associated with disorders caused by allelic variants affecting protein function. Flavin-dependent proteins also play an important role in the biosynthesis of other essential cofactors and hormones such as coenzyme A, coenzyme Q, heme, pyridoxal 5'-phosphate, steroids and thyroxine. Moreover, they are important for the regulation of folate metabolites by using tetrahydrofolate as cosubstrate in choline degradation, reduction of N-5.10-methylenetetrahydrofolate to N-5-methyltetrahydrofolate and maintenance of the catalytically competent form of methionine synthase. These flavoenzymes are discussed in detail to highlight their role in health and disease.

Desferrioxamine treatment of porphyria cutanea tarda in a patient with HIV and chronic renal failure

Porphyria cutanea tarda (PCT) can occur in HIV patients. Current evidence suggests that HIV infection may interfere with the hepatic cytochrome oxidase system, leading to porphyrin metabolism impairment. Moreover, chronic hemodialysis in renal failure may be a risk factor for PCT. In addition to the contributory factors for PCT associated to HIV infection, it is possible that porphyrin accumulation secondary to renal failure may play a role in the expression of this disease. We report a case of PCT in an HIV-1 infected patient under blood dialysis, refractory to antimalarials and controlled with desferrioxamine.

Erythroid heme biosynthesis and its disorders

Heme, which is composed of iron and the small organic molecule protoporphyrin, is an essential component of hemoglobin as well as a variety of physiologically important hemoproteins. During erythropoiesis, heme synthesis is induced before, and is essential for, globin synthesis. Although all cells possess the ability to synthesize heme, there are distinct differences between regulation of the pathway in developing erythroid cells and all other types of cells. Disorders that compromise the ability of the developing red cell to synthesize heme can have profound medical implications. The biosynthetic pathway for heme and key regulatory features are reviewed herein, along with specific human genetic disorders that arise from defective heme synthesis such as X-linked sideroblastic anemia and erythropoietic protoporphyria.

Gas chromatography-mass spectrometry profiling of steroids in urine of patients with acute intermittent porphyria

OBJECTIVE

Acute intermittent porphyria (AIP) is an autosomal dominant disease that results from a deficiency of hydroxymethylbilane synthase, the third enzyme of the heme biosynthetic pathway. AIP carriers may present acute neurovisceral attacks with hepatic overproduction of heme-precursors. In some patients, remission of the acute symptoms leads to long-term hepatic metabolic abnormalities. In this study, gas chromatography-mass spectrometry (GC/MS) was used to investigate urinary steroid metabolome of AIP patients.

DESIGN AND METHODS

Steroid profiling in urine was performed in a group of AIP patients with biochemically active disease (n=22) and healthy controls (n = 20). Five asymptomatic AIP family carriers were also studied. Commonly used ratios for the evaluation of disturbances in the steroid metabolism were calculated.

RESULTS

We found that etiocholanolone/androsterone and tetrahydrocortisol/5α-tetrahydrocortisol (THF/5α-THF) metabolic ratios were significantly increased in the urine of AIP patients compared to controls (2.3 ± 0.3 vs 0.8 ± 0.1; p < 0.001 and 2.9 ± 0.7 vs 0.9 ± 0.1; p < 0.01). The (THF+5α-THF)/tetrahydrocortisone ratio was reduced among the AIP patients (p < 0.01). Quantification of the steroid absolute concentrations showed that these variations were due to a decrease of the 5α metabolites. Other ratios, like cortisol/cortisone and 6β-hydroxycortisol/cortisol in the free steroid fraction did not show differences between patients and controls. All ratios were normal among the family carriers.

CONCLUSION

A significant number of AIP patients present a basal decrease of steroid 5α-reductase activity in the liver. The deficiency may be related to malnutrition and hepatic energy misbalance associated with active AIP. Urinary steroid profiling by GC/MS may be a valuable tool to assess hepatic metabolome in AIP.

Quantitative structural insight into human variegate porphyria disease

Defects in the human protoporphyrinogen oxidase (hPPO) gene, resulting in ~50% decreased activity of hPPO, is responsible for the dominantly inherited disorder variegate porphyria (VP). To understand the molecular mechanism of VP, we employed the site-directed mutagenesis, biochemical assays, structural biology, and molecular dynamics simulation studies to investigate VP-causing hPPO mutants. We report here the crystal structures of R59Q and R59G mutants in complex with acifluorfen at a resolution of 2.6 and 2.8 Å. The r.m.s.d. of the Cα atoms of the active site structure of R59G and R59Q with respect to the wild-type was 0.20 and 0.15 Å, respectively. However, these highly similar static crystal structures of mutants with the wild-type could not quantitatively explain the observed large differences in their enzymatic activity. To understand how the hPPO mutations affect their catalytic activities, we combined molecular dynamics simulation and statistical analysis to quantitatively understand the molecular mechanism of VP-causing mutants. We have found that the probability of the privileged conformations of hPPO can be correlated very well with the k(cat)/K(m) of PPO (correlation coefficient, R(2) > 0.9), and the catalytic activity of 44 clinically reported VP-causing mutants can be accurately predicted. These results indicated that the VP-causing mutation affect the catalytic activity of hPPO by affecting the ability of hPPO to sample the privileged conformations. The current work, together with our previous crystal structure study on the wild-type hPPO, provided the quantitative structural insight into human variegate porphyria disease.

Partial protoporphyrinogen oxidase (PPOX) gene deletions, due to different Alu-mediated mechanisms, identified by MLPA analysis in patients with variegate porphyria

Variegate porphyria (VP) is an autosomal dominantly inherited hepatic porphyria. The genetic defect in the PPOX gene leads to a partial defect of protoporphyrinogen oxidase, the penultimate enzyme of heme biosynthesis. Affected individuals can develop cutaneous symptoms in sun-exposed areas of the skin and/or neuropsychiatric acute attacks. The identification of the genetic defect in VP families is of crucial importance to detect the carrier status which allows counseling to prevent potentially life threatening neurovisceral attacks, usually triggered by factors such as certain drugs, alcohol or fasting.In a total of 31 Swedish VP families sequence analysis had identified a genetic defect in 26. In the remaining five families an extended genetic investigation was necessary. After the development of a synthetic probe set, MLPA analysis to screen for single exon deletions/duplications was performed.We describe here, for the first time, two partial deletions within the PPOX gene detected by MLPA analysis. One deletion affects exon 5 and 6 (c.339-197_616+320del1099) and has been identified in four families, most probably after a founder effect. The other extends from exon 5 to exon 9 (c.339-350_987+229del2609) and was found in one family. We show that both deletions are mediated by Alu repeats.Our findings emphasize the usefulness of MLPA analysis as a complement to PPOX gene sequencing analysis for comprehensive genetic diagnostics in patients with VP.

Porphyric neuropathy

Porphyric neuropathy often poses a diagnostic dilemma; it is typically associated with the hepatic porphyrias, characterized by acute life-threatening attacks of neurovisceral symptoms that mimic a range of acute medical and psychiatric conditions. The development of acute neurovisceral attacks is responsive to environmental factors, including drugs, hormones, and diet. This chapter reviews the clinical manifestations, genetics, pathophysiology, and mechanisms of neurotoxicity of the acute hepatic porphyrias. While the etiology of the neurological manifestations in the acute porphyrias remains undefined, the main hypotheses include toxicity of porphyrin precursors and deficiency of heme synthesis. These hypotheses will be discussed with reference to novel experimental models of porphyric neuropathy.

Molecular and functional analysis of the C-terminal region of human erythroid-specific 5-aminolevulinic synthase associated with X-linked dominant protoporphyria (XLDPP)

Frameshift mutations in the last coding exon of the 5-aminolevulinate synthase (ALAS) 2 gene were described to activate the enzyme causing increased levels of zinc- and metal-free protoporphyrin in patients with X-linked dominant protoporphyria (XLDPP). Only two such so-called gain-of-function mutations have been reported since the description of XLDPP in 2008. In this study of four newly identified XLDPP families, we identified two novel ALAS2 gene mutations, a nonsense p.Q548X and a frameshift c.1651-1677del26bp, along with a known mutation (delAGTG) found in two unrelated families. Of relevance, a de novo somatic and germinal mosaicism was present in a delAGTG family. Such a phenomenon may explain the high proportion of this mutation in XLDPP worldwide. Enhancements of over 3- and 14-fold in the catalytic rate and specificity constant of purified recombinant XLDPP variants in relation to those of wild-type ALAS2 confirmed the gain of function ascribed to these enzymes. The fact that both p.Q548X and c.1651-1677del26bp are located in close proximity and upstream from the two previously described mutations led us to propose the presence of a large gain-of-function domain within the C-terminus of ALAS2. To test this hypothesis, we generated four additional nonsense mutants (p.A539X, p.G544X, p.G576X and p.V583X) surrounding the human XLDPP mutations and defined an ALAS2 gain-of-function domain with a minimal size of 33 amino acids. The identification of this gain-of-function domain provides important information on the enzymatic activity of ALAS2, which was proposed to be constitutively inhibited, either directly or indirectly, through its own C-terminus.

Establishing a network of specialist Porphyria centres - effects on diagnostic activities and services

BACKGROUND

The porphyrias are a heterogeneous group of rare metabolic diseases. The full spectrum of porphyria diagnostics is usually performed by specialized porphyria laboratories or centres. The European Porphyria Initiative (EPI), a collaborative network of porphyria centres formed in 2001, evolved in 2007 into the European Porphyria Network (EPNET), where participating centres are required to adhere to agreed quality criteria. The aim of this study was to examine the state and distribution of porphyria diagnostic services in 2009 and to explore potential effects of increased international collaboration in the field of these rare diseases in the period 2006-2009.

METHODS

Data on laboratory, diagnostic and clinical activities and services reported to EPI/EPNET in yearly activity reports during 2006 through 2009 were compared between reporting centres, and possible time trends explored.

RESULTS

Thirty-five porphyria centres from 22 countries, five of which were non-European associate EPNET members, filed one or more activity reports to EPI/EPNET during the study period. Large variations between centres were observed in the analytical repertoire offered, numbers of analyses performed and type and number of staff engaged. The proportion of centres fulfilling the minimum criteria set by EPNET to be classified as a specialist porphyria centre increased from 80% to 94% during the study period.

CONCLUSIONS

Porphyria services are unevenly distributed, and some areas are probably still lacking in specialized porphyria services altogether. However, improvements in the quality of diagnostic services provided by porphyria centres participating in EPI/EPNET were observed during 2006 through 2009.

The porphyrias: advances in diagnosis and treatment

The inborn errors of heme biosynthesis, the porphyrias, are 8 genetically distinct metabolic disorders that can be classified as “acute hepatic,” “hepatic cutaneous,” and “erythropoietic cutaneous” diseases. Recent advances in understanding their pathogenesis and molecular genetic heterogeneity have led to improved diagnosis and treatment. These advances include DNA-based diagnoses for all the porphyrias, new understanding of the pathogenesis of the acute hepatic porphyrias, identification of the iron overload-induced inhibitor of hepatic uroporphyrin decarboxylase activity that causes the most common porphyria, porphyria cutanea tarda, the identification of an X-linked form of erythropoietic protoporphyria due to gain-of-function mutations in erythroid-specific 5-aminolevulinate synthase (ALAS2), and new and experimental treatments for the erythropoietic prophyrias. Knowledge of these advances is relevant for hematologists because they administer the hematin infusions to treat the acute attacks in patients with the acute hepatic porphyrias, perform the chronic phlebotomies to reduce the iron overload and clear the dermatologic lesions in porphyria cutanea tarda, and diagnose and treat the erythropoietic porphyrias, including chronic erythrocyte transfusions, bone marrow or hematopoietic stem cell transplants, and experimental pharmacologic chaperone and stem cell gene therapies for congenital erythropoietic protoporphyria. These developments are reviewed to update hematologists on the latest advances in these diverse disorders.

The porphyrias: advances in diagnosis and treatment

The inborn errors of heme biosynthesis, the porphyrias, are 8 genetically distinct metabolic disorders that can be classified as "acute hepatic," "hepatic cutaneous," and "erythropoietic cutaneous" diseases. Recent advances in understanding their pathogenesis and molecular genetic heterogeneity have led to improved diagnosis and treatment. These advances include DNA-based diagnoses for all the porphyrias, new understanding of the pathogenesis of the acute hepatic porphyrias, identification of the iron overload-induced inhibitor of hepatic uroporphyrin decarboxylase activity that causes the most common porphyria, porphyria cutanea tarda, the identification of an X-linked form of erythropoietic protoporphyria due to gain-of-function mutations in erythroid-specific 5-aminolevulinate synthase (ALAS2), and new and experimental treatments for the erythropoietic porphyrias. Knowledge of these advances is relevant for hematologists because they administer the hematin infusions to treat the acute attacks in patients with the acute hepatic porphyrias, perform the chronic phlebotomies to reduce the iron overload and clear the dermatologic lesions in porphyria cutanea tarda, and diagnose and treat the erythropoietic porphyrias, including chronic erythrocyte transfusions, bone marrow or hematopoietic stem cell transplants, and experimental pharmacologic chaperone and stem cell gene therapies for congenital erythropoietic protoporphyria. These developments are reviewed to update hematologists on the latest advances in these diverse disorders.

Photosensitivity disorders in children: part I

Photosensitivity disorders in children encompass a diverse group of diseases. Compared to adult patients, underlying systemic disorders, including genetic or metabolic defects, are common causes in pediatric photosensitivity disorders. Photosensitivity in a child should be suspected if the child develops a sunburn reaction in sun-exposed sites after limited sun exposure. Diagnosis of a photodermatosis is made based on careful history taking and a physical examination. Early recognition and prompt diagnosis are essential to minimize long-term complications associated with inadequate photoprotection. In part I of this continuing medical education article, immunologically mediated photodermatoses, photodermatoses caused by exogenous photosensitizers, and the cutaneous porphyrias will be covered.

Isolation of an X-factor-dependent but porphyrin-positive Escherichia coli from urine of a patient with hemorrhagic cystitis

An Escherichia coli isolate was recovered from a 92-year-old female patient with urinary tract infection. Gram-stained preparation of the urine sediment manifested some gram-negative rod-shaped cells, and the urine specimen culture yielded nonhemolytic colonies on sheep blood agar plate. However, no visible colonies appeared on modified Drigalski agar plate. The isolate was finally identified as an X-factor-dependent E. coli. The interesting finding was that the isolate revealed a positive reaction for porphyrin test despite the requirement of hemin. This finding suggested that some pyrrol-ring-containing porphyrin compounds or fluorescent porphyrins had been produced as chemical intermediates in the synthetic pathway from δ-amino-levulinic acid (ALA), although the isolate should be devoid of synthesizing hems from ALA. This was the first clinical isolation of such a strain, indicating that the E. coli isolate should possess incomplete synthetic pathways of hems from ALA.

Assessing nutritional status of acute intermittent porphyria patients

BACKGROUND

Acute intermittent porphyria (AIP) is a metabolic disease of haem synthesis, whose haem precursors may accumulate in the body. A well-balanced diet may prevent the symptoms, so that porphyric patients should be monitored closely during therapy for possible complications concerning any progression of acute porphyria. The aim was to evaluate the nutritional status of patients with AIP and to assess their compliance with nutritional recommendations, comparing the findings with a control group and assessing any possible nutritional deficiency.

MATERIAL AND METHODS

Sixteen patients with AIP and a control group were evaluated by means of a lifestyle questionnaire, the Nutrition Screening Initiative checklist and a dietary questionnaire. The following diet quality indicators were calculated: animal and vegetal proteins, protein quality index, PUFA/SFA and MUFA + PUFA/SFA ratios, insoluble dietary fibre (DF)/total DF, soluble DF/total DF and insoluble DF/soluble DF ratios, thiamine, riboflavin and niacin density and the vitamin B6/protein ratio.

STATISTICAL METHODS

Differences in continuous variables were compared using the unpaired Student's t-test and the chi-square test for nonparametric variables. The odds ratio (OR) of malnutrition was also used.

RESULTS

Our patients showed a low intake of carbohydrates, a high lipid intake and very high protein intake, and accompanied by an inadequate intake of zinc, folic acid and tocopherol, increasing the risk of malnutrition for energy, Ca, Fe, Mg, K, folic acid and tocopherols.

CONCLUSIONS

The patients with AIP studied individually show an increased risk of malnutrition and, given the potential increase of oxidative stress in patients with porphyria, it is recommended that they should increase their intake of carbohydrates, minerals and antioxidant nutrients.