PICO questions and DELPHI methodology for improving the management of patients with acute hepatic porphyria

BACKGROUND

Acute hepatic porphyrias (AHPs) are a group of rare diseases that encompasses acute intermittent porphyria, variegate porphyria, hereditary coproporphyria, and 5-aminolaevulinic acid dehydratase deficiency porphyria. Symptoms of AHP are nonspecific which, together with its low prevalence, difficult the diagnosis and follow-up of these patients.

MATERIAL AND METHODS

This project used DELPHI methodology to answer PICO questions related to management of patients with AHPs. The objective was to reach a consensus among multidisciplinary porhyria experts providing answers to those PICO questions for improving diagnosis and follow-up of patients with AHP.

RESULTS

Ten PICO questions were defined and grouped in four domains: 1. Biochemical diagnosis of patients with AHP. 2. Molecular tests for patients with AHP. 3. Follow-up of patients with AHP. 4. Screening for long-term complications of patients with AHP.

CONCLUSIONS

PICO questions and DELPHI methodology have provided a consensus on relevant and controversial issues for improving the management of patients with AHP.

Acute hepatic porphyrias: Recommendations for diagnosis and management with real-world examples

Acute hepatic porphyria (AHP) is a group of four rare inherited diseases, each resulting from a deficiency in a distinct enzyme in the heme biosynthetic pathway. Characterized by acute neurovisceral symptoms that may mimic other medical and psychiatric conditions, lack of recognition of the disease often leads to a delay in diagnosis and initiation of effective treatment. Biochemical testing for pathway intermediates that accumulate when the disease is active forms the basis for screening and establishing a diagnosis. Subsequent genetic analysis identifies the pathogenic variant, supporting screening of family members and genetic counseling. Management of AHP involves avoidance of known exogenous and hormonal triggers, symptomatic treatment, and prevention of recurrent attacks. Here we describe six case studies from our own real-world experience to highlight current recommendations and challenges associated with the diagnosis and long-term management of the disease.

Prevalence of Undiagnosed Acute Hepatic Porphyria in Cyclic Vomiting Syndrome and Overlap in Clinical Symptoms

BACKGROUND AND AIMS

Acute hepatic porphyria (AHP) presents with nausea and vomiting and can mimic cyclic vomiting syndrome (CVS). The prevalence of AHP in CVS and overlap in clinical symptomatology is not known. We thus sought to determine the prevalence of pathogenic variants for AHP and characterize symptom overlap between CVS and AHP.

METHODS

We conducted a cross-sectional study of 234 CVS patients using Rome criteria. Patients were eligible for AHP genetic testing if they had recurrent episodes of severe, diffuse abdominal pain with ≥ 2 of the following-peripheral nervous system (muscle weakness/aching, numbness, tingling), central nervous system (confusion, anxiety, seizures, hallucinations), autonomic nervous system (hyponatremia, tachycardia, hypertension, constipation) symptoms, red/brownish urine, or blistering skin lesions on sun-exposed areas. A family history of AHP or elevated urinary porphobilinogen (PBG)/aminolaevulinic acid (ALA) were also criteria for genetic testing and was performed using a 4-gene panel.

RESULTS

Mean age was 38.7 ± 14.5 years, 180 (76.9%) were female and 200 (85.5%) were Caucasian. During a CVS attack, 173 (92%) reported abdominal pain, 166 (87.2%) had peripheral nervous system, 164 (86.8%) had central nervous system and 173 (92) % had autonomic symptoms. Ninety-one eligible patients completed genetic testing. None were positive for AHP but two had variants of uncertain significance (VUS) in the HMBS gene.

CONCLUSIONS

There is a high prevalence of non-gastrointestinal symptoms in CVS, like AHP, which is important for clinicians to recognize. AHP was not detected in this study and larger studies are warranted to ascertain its prevalence.

Spotlight on Givosiran as a Treatment Option for Adults with Acute Hepatic Porphyria: Design, Development, and Place in Therapy

Small interfering ribonucleic acids [siRNAs] are short ribonucleic acid (RNA) fragments cleaved from double-stranded RNA molecules that target and bind to specific sequences on messenger RNA (mRNA), leading to their destruction. Therefore, the siRNA down-regulates the formation of selected mRNAs and their protein products. Givosiran is one such siRNA that uses this mechanism to treat acute hepatic porphyrias. Acute hepatic porphyrias are a group of rare, inherited metabolic disorders, characterized by acute potentially life-threatening attacks as well as chronic symptoms with a negative impact on quality of life. It has four types, each associated with distinct enzyme defects in the heme biosynthesis pathway in the liver. By targeting the expression of hepatic 5-aminolevulinic acid [ALA] synthase-1 [ALAS1], givosiran can down-regulate levels of toxic metabolites, leading to biochemical and clinical improvement. Givosiran selectively targets hepatocytes due to its linkage to N-acetylgalactosamine (GalNac) leading to its selective uptake via asialoglycoprotein receptors (ASGPR). We provide an up-to-date literature review regarding givosiran in the context of a clinical overview of the porphyrias, an overview of siRNAs for therapy of human disorders, the design and development of givosiran, key clinical trial results of givosiran for prevention of acute porphyric attacks, emerging concerns regarding chronic use of givosiran, and the overall management of acute hepatic porphyrias. These insights are important not only for the management of acute hepatic porphyrias but also for the emerging field of siRNAs and their role in novel therapies for various diseases.

Acute Hepatic Porphyrias: "Purple Flags"-Clinical Features That Should Prompt Specific Diagnostic Testing

BACKGROUND

Porphyrias are a group of rare diseases leading to dysregulation in heme biosynthesis and the accumulation of heme precursors, including porphyrinogens, which in their oxidized states [porphyrins] are reddish or purple. Acute hepatic porphyrias (AHP) comprise four diseases that cause acute debilitating neurovisceral attacks. Despite diagnostic advances, AHP is often undiagnosed or misdiagnosed due to a lack of disease awareness, low clinical suspicion, variable presentation, and nonspecific symptoms that mimic more common diseases. Delays in diagnosis and treatment increase the risk of serious acute and chronic complications.

METHODS

In order to assess whether symptoms alone or in combination might be utilized as important indicators or "purple flags" that, when present, should alert clinicians to suspect AHP and pursue specific diagnostic testing, we conducted a comprehensive review of the literature on AHP, including cohort studies and case reports over two epochs, from 1980 to 2006 and from 2012 to 2018.

RESULTS

We found that severe abdominal pain, with or without acute central nervous system manifestations and peripheral neuropathy, continues to be the most frequent symptom. Hyponatremia, change in urine color, and certain chronic symptoms were also identified as features that should raise suspicion of AHP. To improve diagnosis of AHP, clinicians need to take a broad perspective, including demographic data and medical history, into consideration.

CONCLUSIONS

The clinical features of AHP continue to be severe pain, especially pain in the abdomen. Other features that should raise suspicion are autonomic, peripheral, or central neuropathies, hyponatremia, and red-purple urine color.

Porphyria attacks in prepubertal children and adolescents

CONTEXT

The clinical and laboratory features of dominant acute hepatic porphyrias (AHPs) in prepubertal children and adolescents have not been well established.

OBJECTIVE

To evaluate clinical and laboratory features of AHPs in prepubertal children and adolescents compared to adults.

DATA SOURCES

OVID (Embase Classic+Embase and MEDLINE), Scopus, and Google Scholar.

STUDY SELECTION

Studies describing symptomatic children or adolescents (<18 years old) with increased urinary porphobilinogen were included.

DATA EXTRACTION

Two reviewers independently extracted the data, with a third reviewer arbitrating discrepancies.

RESULTS

100 studies were included describing 112 patients (26 prepubertal children and 86 adolescents). Differences were found between prepubertal children and adolescents regarding sex distribution (female-to-male ratio: 1:2 vs. 4:1), clinical manifestations, and concomitant clinical manifestations.

LIMITATIONS

There was variation in the methods used to diagnose porphyria attacks across studies, and some elements of the quality of individual studies were unclear.

CONCLUSIONS

Prepubertal children with AHPs and porphyria attacks presented with distinct demographic and clinical characteristics from adolescents and adults. Nearly two-thirds of the affected children were males, and about half had a concomitant medical condition that can constitutively upregulate hepatic δ-aminolevulinic acid synthase-1. Adolescents were comparable to adults in almost all respects.

Biochemical Diagnosis of Acute Hepatic Porphyria: Updated Expert Recommendations for Primary Care Physicians

Acute hepatic porphyria (AHP) is a group of rare, metabolic diseases where patients can experience acute neurovisceral attacks, chronic symptoms, and long-term complications. Diagnostic biochemical testing is widely available and effective, but a substantial time from symptom onset to diagnosis often delays treatment and increases morbidity. A panel of laboratory scientists and clinical AHP specialists collaborated to produce recommendations on how to enhance biochemical diagnosis of AHP in the USA. AHP should be considered in the differential diagnosis of unexplained abdominal pain, the most common symptom, soon after excluding common causes. Measurement of porphobilinogen (PBG) and porphyrins in a random urine sample, with results normalized to creatinine, is recommended as an effective and cost-efficient initial test for AHP. Delta-aminolevulinic acid testing may be included but is not essential. The optimal time to collect a urine sample is during an attack. Substantial PBG elevation confirms an AHP diagnosis and allows for prompt treatment initiation. Additional testing can determine AHP subtype and identify at-risk family members. Increased awareness of AHP and correct diagnostic methods will reduce diagnostic delay and improve patient outcomes.

The clinical importance of early acute hepatic porphyria diagnosis: a national cohort

Acute hepatic porphyria (AHP) attacks begin with abdominal pain and can progress to severe life-threatening conditions. Early diagnosis and treatment may prevent these complications. We investigated the difference between the severity of porphyria attacks before and after porphyria diagnosis. A retrospective study including AHP patients hospitalized for an acute attack in Israel during a 15-year period. Diagnosis of an attack was based on typical clinical symptoms accompanied by at least one documented elevated urinary porphobilinogen above fourfold of normal values. The primary outcome was intensive care unit (ICU) admissions. Secondary outcomes included the length of hospital stay, severe hyponatremia, seizures, and psychiatric symptoms. 42 attacks in 9 patients were included. Most attacks occurred in women (78.6%) and in acute intermittent porphyria patients (76.2%). The mean age of attack was 26.5 (± 6.3) years. Attacks following porphyria diagnosis had a lower prevalence of ICU admission (3.3% versus 75.0%, p < 0.001), seizures (0% versus 50.0%, p < 0.001), psychiatric symptoms (23.3% versus 66.7%, p = 0.01), severe hyponatremia (16.7% versus 83.3%, p < 0.001), and median length of hospital stay (5 versus 11.0 days, p < 0.001). These results remained significant after simple univariate logistic regression for ICU admission [odds ratio (OR) 0.01, 95% confidence interval (CI) 0.00-0.12], prolonged hospital stay (OR 0.08, 95% CI 0.01-0.41), seizures or neurological symptoms (OR 0.06, 95% CI 0.01-0.30), and severe hyponatremia (OR 0.02, 95% CI 0.00-0.20). Previously diagnosed AHP patients have a significantly milder attack course as compared to previously undiagnosed patients. Family screening following sentinel cases might prevent severe AHP attacks.

Development of siRNA Therapeutics for the Treatment of Liver Diseases

Small interfering RNA (siRNA)-based therapeutics holds the promise to treat a wide range of human diseases that are currently incurable using conventional therapies. Most siRNA therapeutic efforts to date have focused on the treatment of liver diseases due to major breakthroughs in the development of efficient strategies for delivering siRNA drugs to the liver. Indeed, the development of lipid nanoparticle-formulated and GalNAc-conjugated siRNA therapeutics has resulted in recent FDA approvals of the first siRNA-based drugs, patisiran for the treatment of hereditary transthyretin amyloidosis and givosiran for the treatment of acute hepatic porphyria, respectively. Here, we describe the current strategies for delivering siRNA drugs to the liver and summarize recent advances in clinical development of siRNA therapeutics for the treatment of liver diseases.

Detecting rare diseases in electronic health records using machine learning and knowledge engineering: Case study of acute hepatic porphyria

BACKGROUND

With the growing adoption of the electronic health record (EHR) worldwide over the last decade, new opportunities exist for leveraging EHR data for detection of rare diseases. Rare diseases are often not diagnosed or delayed in diagnosis by clinicians who encounter them infrequently. One such rare disease that may be amenable to EHR-based detection is acute hepatic porphyria (AHP). AHP consists of a family of rare, metabolic diseases characterized by potentially life-threatening acute attacks and chronic debilitating symptoms. The goal of this study was to apply machine learning and knowledge engineering to a large extract of EHR data to determine whether they could be effective in identifying patients not previously tested for AHP who should receive a proper diagnostic workup for AHP.

METHODS AND FINDINGS

We used an extract of the complete EHR data of 200,000 patients from an academic medical center and enriched it with records from an additional 5,571 patients containing any mention of porphyria in the record. After manually reviewing the records of all 47 unique patients with the ICD-10-CM code E80.21 (Acute intermittent [hepatic] porphyria), we identified 30 patients who were positive cases for our machine learning models, with the rest of the patients used as negative cases. We parsed the record into features, which were scored by frequency of appearance and filtered using univariate feature analysis. We manually choose features not directly tied to provider attributes or suspicion of the patient having AHP. We trained on the full dataset, with the best cross-validation performance coming from support vector machine (SVM) algorithm using a radial basis function (RBF) kernel. The trained model was applied back to the full data set and patients were ranked by margin distance. The top 100 ranked negative cases were manually reviewed for symptom complexes similar to AHP, finding four patients where AHP diagnostic testing was likely indicated and 18 patients where AHP diagnostic testing was possibly indicated. From the top 100 ranked cases of patients with mention of porphyria in their record, we identified four patients for whom AHP diagnostic testing was possibly indicated and had not been previously performed. Based solely on the reported prevalence of AHP, we would have expected only 0.002 cases out of the 200 patients manually reviewed.

CONCLUSIONS

The application of machine learning and knowledge engineering to EHR data may facilitate the diagnosis of rare diseases such as AHP. Further work will recommend clinical investigation to identified patients' clinicians, evaluate more patients, assess additional feature selection and machine learning algorithms, and apply this methodology to other rare diseases. This work provides strong evidence that population-level informatics can be applied to rare diseases, greatly improving our ability to identify undiagnosed patients, and in the future improve the care of these patients and our ability study these diseases. The next step is to learn how best to apply these EHR-based machine learning approaches to benefit individual patients with a clinical study that provides diagnostic testing and clinical follow up for those identified as possibly having undiagnosed AHP.

Hepatocellular carcinoma in acute hepatic porphyrias: A Damocles Sword

Porphyrias are inherited diseases with low penetrance affecting the heme biosynthesis pathway. Acute intermittent porphyria (AIP), variegate porphyria (VP) and hereditary coproporphyria (HCP) together constitute the acute hepatic porphyrias (AHP). These diseases have been identified as risk factors for primary liver cancers (PLC), mainly hepatocellular carcinoma (HCC: range 87-100%) but also cholangiocarcinoma, alone or combination with HCC. In AHP, HCC annual incidence rates range from 0.16 to 0.35% according to the populations studied. Annual incidence rates are higher in Swedish and Norwegian patients, due to a founder effect. It increases above age 50. The pathophysiology could include both direct toxic effects of heme precursors, particularly δ-aminolevulinic acid (ALA), compound heterozygosity for genes implied in heme biosynthesis pathway or the loss of oxidative stress homeostasis due to a relative lack of heme. The high HCC incidence justifies radiological surveillance in AHP patients above age 50. Efforts are made to find new biological non-invasive markers. In this respect, we describe here the first report of PIVKA-II clinical utility in the follow-up of an AIP patient that develop an HCC. In this manuscript we reviewed the epidemiology, the physiopathology, and the screening strategy of HCC in AHP.

Acute hepatic porphyrias: Current diagnosis & management

Each of the four acute hepatic porphyrias is due to mutation of an enzyme in the heme biosynthetic pathway. The accumulation of pathway intermediates that occur most notably when these diseases are active is the basis for screening and establishing a biochemical diagnosis of these rare disorders. Measurement of enzyme activities and especially DNA testing also are important for diagnosis. Suspicion of the diagnosis and specific testing, particularly measurement of urinary porphobilinogen, are often delayed because the symptoms are nonspecific, even when severe. Urinary porphyrins are also measured, but their elevation is much less specific. If porphobilinogen is elevated, second line testing will establish the type of acute porphyria. DNA testing identifies the familial mutation and enables screening of family members. Management includes removal of triggering factors whenever possible. Intravenous hemin is the most effective treatment for acute attacks. Carbohydrate loading is sometimes used for mild attacks. Cyclic attacks, if frequent, can be prevented by a GnRH analogue. Frequent noncyclic attacks are sometime preventable by scheduled (e.g. weekly) hemin infusions. Long term complications may include chronic pain, renal impairment and liver cancer. Other treatments, including RNA interference, are under development.

THINK PORPHYRIA: CASE REPORT AND REVIEW OF LITERATURE

Porphyrias are a group of rare disorders caused by enzyme defects in haem biosynthesis pathway. Acute intermittent porphyria is the most common hepatic porphyria. The disorder presents with severe neuropathic abdominal pain that can be accompanied by a wide range of gastrointestinal, psychiatric and neurological symptoms, making the diagnosis clarification very challenging. We report a case of a 27-year-old female patient who presented with acute abdominal pain, vomiting and marked hyponatremia, developed seizures and disorientation, and eventually required intensive care unit treatment to maintain breathing. Her symptoms were initially misinterpreted as a functional gastrointestinal disorder, thus delaying the needed specific treatment. She was diagnosed a week after the initial hospital admission, and her condition improved after receiving treatment with intravenous glucose and haemin. For patients with acute neurovisceral attacks, early clinical recognition is essential. Severe hyponatremia, urine that develops orange colour on exposure to light and gastrointestinal symptom combination with neurologic symptoms are three valuable clues that may lead to the right diagnosis faster. Pathophysiology of hyponatremia in case of acute intermittent porphyria in only partly understood and can be associated with syndrome of inappropriate antidiuretic hormone secretion, gastrointestinal or renal sodium loss.

[Hepatic porphyrias with cutaneous symptoms]

Hepatic porphyrias with cutaneous symptoms Cutaneous symptoms of porphyrias are initiated from a phototoxic reaction caused by sunlight and circulating porphyrins in the vascular walls of the skin. This leads in fragility, blistering and scarring of the skin on light-exposed areas. There are approximately 200 patients having hepatic porphyrias with cutaneous symptoms in Finland. Cutaneous symptoms of variegate porphyria and porphyria cutanea tarda are indistinguishable, but an effective treatment is available only for the latter. Differential diagnosis is important due to acute episodes occurring in variegate porphyria.

Syndrome of Inappropriate Antidiuretic Hormone Secretion Associated with Coproporphyria: Case Report and Review of Literature

OBJECTIVE

To remind physicians to consider the hepatic porphyrias in the differential diagnosis of the syndrome of inappropriate antidiuretic hormone secretion.

METHODS

We present a case report of a patient seen in the hospital for severe hyponatremia, who was discovered to have the syndrome of inappropriate antidiuretic hormone secretion attributable to coproporphyria. Results of laboratory tests of the patient and her family are presented.

RESULTS

A 54-year-old woman was seen in the hospital because of severe hyponatremia accompanied by generalized seizures. Her serum sodium concentration was 112 mEq/L, with concomitant serum and urine osmolalities of 235 and 639 mOsm/kg, respectively. Renal, thyroid, and adrenal functions were normal. Brain, chest, abdominal, and pelvic imaging studies were negative for occult malignant disease. Urinary excretions of porphobilinogen and aminolevulinic acid were substantially elevated. Results of follow-up urine, plasma, and fecal porphyrin studies were consistent with coproporphyria. Results of porphyrin metabolic studies of the patient's family showed normal findings in her parents and a minimally increased fecal coproporphyrin concentration and urinary uroporphyrin excretion in her sister.

CONCLUSION

An endocrinology consultation is often requested for patients with hyponatremia. It is important to consider the acute hepatic porphyrias in the differential diagnosis, even though these are rare disorders and the family history may not always be helpful because of the high frequency of asymptomatic carriers.

Unusual Manifestation of Acute Hepatic Porphyria in Pregnancy

A 22-year-old para I/gravida II developed psychiatric symptoms at 8 weeks of gestation. Subsequently neurological symptoms with seizures developed leading to a status epilepticus with continuing seizures at week 14. Anticonvulsive therapy had little effect in alleviating the seizures and the condition of the patient rapidly deteriorated. A sudden reddening of her urine lead to the diagnosis of acute hepatic porphyria confirmed by laboratory tests. After extensive discussion with the patient's family it was decided to terminate the pregnancy at week 16. Within hours after pregnancy termination the seizures stopped and the patient recovered without any neurological deficits. Acute hepatic porphyria can be triggered by pregnancy and usually presents with gastrointestinal symptoms and personality changes. In its rare neurological manifestation it can lead to untreatable convulsions which leave no option but to terminate the pregnancy.

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.

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.

Variegate porphyria presenting with acute autonomic dysfunction, intussusception and renal infarction

A 48-year-old man presented with abdominal pain, constipation and irritability one month after starting phenytoin treatment for a generalized seizure. He was hypertensive, tachycardic (BP 174/98, heart rate (HR) 100 bpm supine) and hypovolaemic. Abdominal CT demonstrated transient jejunal intussusception and infarction of the left kidney. Urinary porphobilinogen levels were increased and genetic analysis confirmed the diagnosis of variegate porphyria. Because of ongoing postural hypotension, the patient underwent further autonomic investigations. Levels of blood pressure (MBP), HR and muscle sympathetic activity (MSNA) were increased during the acute attack compared to recovery (131 versus 105 mmHg, 100 versus 60 bpm, 88 versus 26 bursts min(-1)). HR and MSNA did not increase during phase II Valsalva, whereas stroke volume (SV) decays were exaggerated (deltaMBP-56 versus 0-31 mmHg and SV 25% versus 40% baseline). Baroreflex failure causing increased sympathetic activity, decreased sympathetic and parasympathetic rapid responses, loss of splanchnic capacitance and renal salt wasting were the likely mechanisms for postural hypotension. Increased sympathetic activity may also have caused intussusception and focal renal vasoconstriction, both of which may be underdiagnosed causes of abdominal pain in acute porphyria.

Plasma Fluorescence Scanning and Fecal Porphyrin Analysis for the Diagnosis of Variegate Porphyria: Precise Determination of Sensitivity and Specificity with Detection of Protoporphyrinogen Oxidase Mutations as a Reference Standard

Background: Variegate porphyria (VP) is the autosomal dominant disorder associated with deficiency of the enzyme protoporphyrinogen oxidase (PPOX). Plasma fluorescence scanning has been reported to be a more sensitive test for VP than traditional fecal chromatography. Previous comparisons of these techniques predated identification of the PPOX gene. We assessed these techniques in a large group of patients characterized for VP at the DNA level.

Methods: We evaluated all patients for whom the genotype and a plasma scan or fecal porphyrin result were available. Mutations were detected by restriction digest analysis. Plasma fluorescence scanning was conducted according to published methods. Fecal porphyrins were identified and quantified by thin-layer chromatography.

Results: Plasma fluorescence scanning was assessed in 679 patients (205 with VP who were carriers of a PPOX mutation, either with disease symptoms or asymptomatic) and fecal analysis in 473 (190 with VP). Sensitivity and specificity of both tests were higher in adults than in children and higher for adults with disease symptoms than for asymptomatic carriers. In a direct comparison in 168 adults (73 with VP), plasma scanning was significantly more sensitive than fecal porphyrin analysis [sensitivity, 0.96 (95% confidence interval, 0.89–0.99) vs 0.77 (0.66–0.85)]. Fecal coproporphyrin [area under the curve, 0.87 (0.83–0.90)] was a better predictor of VP than protoporphyrin [0.80 (0.76–0.84)].

Conclusions: Plasma scanning is a more sensitive and specific test for VP than fecal porphyrin analysis. Neither test is sensitive in children, and both are less sensitive in asymptomatic carriers than in symptomatic cases. DNA analysis therefore remains the preferred method for the identification of carriers, particularly in children.

[Multifocal nodular fatty infiltration of the liver associated with porphyria and haemochromatosis]

HISTORY AND CLINICAL FINDINGS

A 64-year-old woman suffered from severe fatigue. She was admitted to our outpatient unit for a diagnostic evaluation of multiple liver lesions as well as an adrenal gland tumor. Diabetes mellitus was diagnosed 22 years ago. Clinical evaluation revealed a mild obesity and a facial hypertrichosis.

INVESTIGATIONS

Apart from elevated liver enzymes, serum ferritin and transferrin saturation were increased. Suspected haemochromatosis was verified by genetic analyses. Analyses of a 24 hours urine sample revealed typical constellation of a chronic hepatic porphyria. The liver lesions were diagnosed as multifocal fatty infiltrations using computer tomography. The patient refused a liver biopsy. The tumor of the adrenal gland represented an adenoma without endocrine activity.

TREATMENT AND COURSE

Repeated phlebotomies were performed for the treatment of haemochromatosis. In the following serum ferritin returned to normal and liver enzymes as well as hyperporphyriuria decreased markedly. Diabetes was better controlled due to decrease of insulin requirements, too.

CONCLUSION

This case report highlights the association of hereditary haemochromatosis and chronic hepatic porphyria, which presumably cause multifocal nodal fatty infiltration of the liver. Iron overload is likely the underlying cause, which represents the target for treatment options.

[Porphyria and inappropriate antidiuretic hormone syndrome]

We report the case of a 37-years-old woman with inappropriate antidiuretic hormone syndrome due to an attack of acute porphyria. The patient was admitted to our hospital for abdominal pain, sleepiness and pink urine. Family and personal history were normal. Seven days before the admission the patient had a laparoscopy operation for endometriosis in her left ovary. The patient had had two normal pregnancies. The physical examination was normal, the skin turgor was good and no edema was present, the blood pressure was 140/90 mmHg. Her serum sodium was 114 mEq/L, serum osmolality 243 mOsm/kg, urine sodium 146 mEq/L and urine osmolality 457 mOsm/kg. Values from laboratory examination revealed a normal peripheral haematogram, a normal kidney function, normal liver, adrenal and thyroid function. The urine tested for amino-levulinic acid, coproporphyrin and uroporphyrin was strongly positive. These findings are compatible with Porphyria Variegata or Coproporphyria Hereditary. A diagnosis of Porphyria acute with SIADH was made, and water fluid restriction, i.v. hypertonic saline infusion and furosemide to correct the hyponatremia was begun. In 1966, lesions of the median eminence of the hypothalamus and both hypothalamic -hypophyseal tracts were described in a patient with Porphyria acute intermittent and SIADH. It was suggested that SIADH occurred because of damage to these areas of the brain from excessive exposure to porphyrins.

Modulation of penetrance by the wild-type allele in dominantly inherited erythropoietic protoporphyria and acute hepatic porphyrias

We have recently demonstrated that in an autosomal dominant porphyria, erythropoietic protoporphyria (EPP), the coinheritance of a ferrochelatase (FECH) gene defect and of a wild-type low-expressed FECH allele is generally involved in the clinical expression of EPP. This mechanism may provide a model for phenotype modulation by minor variations in the expression of the wild-type allele in the other three autosomal dominant porphyrias that exhibit incomplete penetrance: acute intermittent porphyria (AIP), variegata porphyria (VP) and hereditary coproporphyria (HC), which are caused by partial deficiencies of hydroxy-methyl bilane synthase (HMBS), protoporphyrinogen oxidase (PPOX) and coproporphyrinogen oxidase (CPO), respectively. Given the dominant mode of inheritance of EPP, VP, AIP and HC, we first confirmed that the 200 overtly porphyric subjects (55 EPP, 58 AIP, 56 VP; 31 HC) presented a single mutation restricted to one allele (20 novel mutations and 162 known mutations). We then analysed the available single-nucleotide polymorphisms (SNPs) present at high frequencies in the general population and spreading throughout the FECH, HMBS, PPOX and the CPO genes in four case-control association studies. Finally, we explored the functional consequences of polymorphisms on the abundance of wild-type RNA, and used relative allelic mRNA determinations to find out whether low-expressed HMBS, PPOX and the CPO alleles occur in the general population. We confirm that the wild-type low-expressed allele phenomenon is usually operative in the mechanism of variable penetrance in EPP, but conclude that this is not the case in AIP and VP. For HC, the CPO mRNA determinations strongly suggest that normal CPO alleles with low-expression are present, but whether this low-expression of the wild-type allele could modulate the penetrance of a CPO gene defect in HC families remains to be ascertained.

Diagnosis and treatment of the hepatic porphyrias

Porphyrias are a peculiar group of diseases resulting from hereditary or acquired partial deficiencies in seven of the eight enzymes in the biosynthetic pathway of heme. Biosynthesis of heme takes place in the erythropoietic system or in the hepatic tissue. Depending on the main location of the enzyme defect, porphyrias can be classified as erythropoietic or hepatic. There are seven basic clinical forms of porphyria related to a deficiency of each of the involved enzymes. Clinical manifestations in porphyria may be neurovisceral or cutaneous. Patients may present with acute attacks (acute porphyrias), cutaneous lesions (cutaneous porphyrias), or both (mixed porphyrias). Study of patients supected of having porphyria should include several steps: 1) clinical evaluation, 2) biochemical study, which enables us to classify the patient to a specific form of porphyria, followed if possible by 3) enzymatic assay(s), and 4) genetic studies to confirm an enzyme deficiency and its level and the causal genetic mutation. Unfortunately no curative treatment is available for any of the porphyrias. However, symptomatic treatments are available and are discussed in this article.

Human hereditary hepatic porphyrias

The human hereditary hepatic porphyrias are diseases due to marked deficiencies of enzymes in the heme biosynthetic pathway. Porphyrias can be classified as either hepatic or erythroid, depending on the major production site of porphyrins or their precursors. The pathogenesis of inherited hepatic porphyrias has now been defined at the molecular level. Some gene carriers are vulnerable to a range of exogenous and endogenous factors, which may trigger neuropsychiatric and/or cutaneous symptoms. Early diagnosis is of prime importance since it makes way for counselling. In this article we present an overview of recent advances on hepatic porphyrias: 5-aminolevulinic acid dehydratase deficiency porphyria, acute intermittent porphyria (AIP), porphyria cutanea tarda (PCT), hereditary coproporphyria (HC), and variegate porphyria (VP).

Molecular, immunological, enzymatic and biochemical studies of coproporphyrinogen oxidase deficiency in a family with hereditary coproporphyria

A 27-year-old woman who had recurrent pain in renal bed since 1998 with increasing character, was stationary admitted. The patient showed dark urine, complained of hair loss and took since 1994 a hormonal oral contraceptive. No photosensitivity was observed. Determinations of urinary porphyrin metabolites in 1998 revealed a porphyria cutanea tarda like excretion pattern with elevations of uro- (1767 nmol/24 hr, normal <29 nmol/24 hr) and heptacarboxyporphyrin (568 nmol/24 hr; normal <4 nmol/24 hr). Follow-up studies in feces showed the characteristics of a hereditary coproporphyria with dominance of coproporphyrin isomer III (total= 1470 nmol/g, isomer III= 93%), (normal: <37 nmol/g, isomer III = 25-35%). The excretion of porphyrin precursors (delta-aminolevulinic acid and porphobilinogen) was increased by taking an ethinylestradiol-cyproteronacetate-preparation, but acute and/or chronic manifestations were not observed. Coproporphyrinogen oxidase activity was decreased to 35% in the patient (normal=138+/-21 pkat/g protein; x+/-s), whereas the activity of red cell uroporphyrinogen decarboxylase was normal. Her mother and both sisters could be verified as heterozygous gene carriers of hereditary coproporphyria by their urinary and fecal excretion parameters and because of reduced coproporphyrinogen oxidase activity up to 50%. The father was normal with respect to his genotype. Molecular analysis revealed a hitherto unknown mutation with the transversion of a cytosine to thymine at nucleotide position 854 in exon 4 of the coproporphyrinogen oxidase gene. The gene defect was confirmed by DGGE in the mother and her three daughters. The investigation of the immunological nature of the defective coproporphyrinogen oxidase gene from the whole family revealed decreased concentrations of coproporphyrinogen oxidase protein in the patient, her mother and her two sisters.

[Coexistence of hereditary coproporphyria and porphyria cutanea tarda: a new form of dual porphyria]

BACKGROUND

Dual porphyrias are characterized by two independent disturbances of porphyrin metabolism.

PATIENT AND METHODS

At first a porphyria cutanea tarda was diagnosed in a 26-year-old female with back pain and red urine. Later a hereditary coproporphyria was ascertained by additional examinations. The metabolites of porphyrin metabolism were analyzed chromatographically. The activities of coproporphyrinogen oxidase and uroporphyrinogen decarboxylase were determined in blood cells. Molecular analysis was carried out by denaturing gradient gel electrophoresis followed by direct sequencing.

RESULTS

Excessive porphyrinuria of 3,128 nmol/24 h (normal < 165 nmol/24 h) with dominance of uro- and heptacarboxyporphyrin (75% of total porphyrins) indicated that the patient suffered from porphyria cutanea tarda. The course of the examination showed an alteration of the constellation with dominance of urinary and fecal coproporphyrin isomer III, which is characteristic for hereditary coproporphyria. Porphyrin precursors and porphyrins increased under the application of ethinylestradiol-cyproteronacetat. The dominance of coproporphyrin III stayed constant in feces besides enhanced urinary uro- and heptacarboxyporphyrin. The activity of the coproporphyrinogen oxidase was diminished to 35%. The uroporphyrinogen decarboxylase in erythrocytes was normal. The mother and both sisters were recognized as heterozygous gene carriers of hereditary coproporphyria in the latent phase by enhanced coproporphyrin with isomer I/III inversion in feces and decrease of the coproporphyrinogen oxidase activity to about 50%. Molecular analyses resulted in a point mutation at exon 4 (854C-->T), which revealed in an amino acid exchange (P258L) in the coproporphyrinogen oxidase protein.

CONCLUSION

The hereditary coproporphyria is caused by a new mutation in the coproporphyrinogen oxidase gene in the case of a dual porphyria with co-existence of porphyria cutanea tarda and hereditary coproporphyria. The sporadic, hepatic porphyria cutanea tarda Type I is induced by estrogens. The large excretory variations reflect the influence of hormonal factors on the porphyria process of hereditary coproporphyria and porphyria cutanea tarda.

Impact of undergraduate medical training on housestaff problem-solving performance: implications for problem-based curricula

This article reports a study comparing the problem-solving performance of housestaff with undergraduate medical training in either conventional or problem-based schools. After reading two clinical cases, residents were required to write differential diagnoses and pathophysiological explanations. Biomedical and clinical knowledge used and reasoning strategies were identified. The results suggest that housestaff performance is influenced by the nature of instruction. Housestaff trained in a conventional curriculum (CC) focused on patient information, separated biomedical from clinical knowledge, and used data-driven strategies. Housestaff from problem-based learning curricula (PBLC) organized their knowledge around generated inferences, integrated biomedical and clinical knowledge, and used hypothesis-driven strategies. Data-driven reasoning appears to be impeded in PBLC, suggesting that PBLC students have difficulties in acquiring problem schemata. Previous investigations also found this pattern to be true for medical students trained in two different curriculum formats. Although all housestaff generated equal numbers of diagnostic hypotheses during the reasoning process, housestaff from the conventional curriculum generated a greater number of accurate hypotheses than residents in PBLC. These results are discussed in relation to assumptions in health professional curricula about the adequacy of hypothetico-deductive methods of reasoning as teaching mechanisms and the need for clinical and biomedical knowledge integration.

Expression and characterization of six mutations in the protoporphyrinogen oxidase gene among Finnish variegate porphyria patients

BACKGROUND

Variegate porphyria (VP) is an inherited disorder of heme biosynthesis that results from a partial deficiency of protoporphyrinogen oxidase (PPOX). Patients with VP may experience acute neurovisceral attacks and cutaneous photosensitivity. To date we have characterized 109 VP patients representing 19 VP families in the Finnish population of 5 million, both biochemically and clinically.

MATERIALS AND METHODS

Mutations were identified by direct sequencing of the patients' genomic DNA. The effect of the mutations was determined by sequencing the reverse transcriptase polymerase chain reaction (RT-PCR) product amplified from total RNA extracted from the patients' lymphoblast cell lines and expressing the mutations in E. coli and COS-1 cells.

RESULTS

Of the six mutations identified in the PPOX gene, three mutations (IVS2-2a-->c, 338G-->C, and 470A-->4C) caused splicing defects, one produced a frameshift (78insC) and two mutations (R152C and L401F) caused amino acid substitutions. In RT-PCR, the IVS2-2a-->c mutation caused a retention of a 36-bp fragment in the 3' end of intron 2, the 338G-->C mutation caused an exon 4 deletion, and the 470A-->C mutation caused an exon 5 deletion with retention of a 19-bp fragment of the 3' end of intron 5. In both prokaryotic and eukaryotic expression systems, the PPOX activities of five mutants were decreased to 0-5% of the normal activity.

CONCLUSIONS

This study describes five novel mutations and one earlier described major mutation among Finnish VP patients. All mutations produced detectable transcripts, but resulted in decreased PPOX activity confirming the causality of the mutations and the biochemical defects in these patients.

Diagnosis of variegate porphyria--hard to get?

Variegate porphyria (VP) is an inherited metabolic disease that results from the partial deficiency of protoporphyrinogen oxidase. In this communication we have used DNA technology in the diagnosis of VP and compared the results with the biochemical and clinical data. To date, we have diagnosed 107 VP patients using either biochemical or DNA techniques or both. In addition, in 106 family members the diagnosis of VP could be excluded. The sensitivity and specificity of the biochemical screening for VP were studied among 38 family members. These individuals were either asymptomatic (n = 19) or had experienced occasional skin symptoms (n = 13), acute attacks (n = 5) or both (n = 1). The sensitivity of urinary and fecal coproporphyrin analysis was 48% and 52%, respectively. The sensitivity of urinary uroporphyrin analysis was 71% and for fecal protoporphyrin 77%. Plasma fluorescence was sensitive in symptomatic patients even in remission, but resulted in false negatives in four asymptomatic patients with normal excretion of porphyrins in the urine. In our series of mutation screening, many new asymptomatic patients were identified, and this demonstrated that DNA analysis is the only reliable way to screen (a)symptomatic patients facilitating correct treatment and proper genetic counselling of family members at risk. Biochemical analyses (e.g. plasma fluorescence, fecal protoporphyrins, urinary copro- and uroporphyrins, porphobilinogen and delta-aminolevulinic acid) are essential when the diagnosis of VP is confirmed at the symptomatic phase.

Erythropoietic and hepatic porphyrias

Porphyrias are divided into erythropoietic and hepatic manifestations. Erythropoietic porphyrias are characterized by cutaneous symptoms and appear in early childhood. Erythropoietic protoporphyria is complicated by cholestatic liver cirrhosis and progressive hepatic failure in 10%, of patients. Acute hepatic porphyrias (delta-aminolaevulinic acid dehydratase deficiency porphyria, acute intermittent porphyria, hereditary coproporphyria and variegate porphyria) are characterized by variable extrahepatic gastrointestinal, neurological-psychiatric and cardiovascular manifestations requiring early diagnosis to avoid life-threatening complications. Acute hepatic porphyrias are pharmacogenetic and molecular regulatory diseases (without porphyrin accumulation) mainly induced by drugs, sex hormones, fasting or alcohol. The disease process depends on the derepression of hepatic delta-aminolaevulinic acid synthase following haem depletion. In contrast to the acute porphyrias, nonacute, chronic hepatic porphyrias such as porphyria cutanea tarda are porphyrin accumulation disorders leading to cutaneous symptoms associated with liver disease, especially caused by alcohol or viral hepatitis. Alcohol, oestrogens, haemodialysis, hepatitis C and AIDS are triggering factors. Porphyria cutanea tarda is the most common porphyria, followed by acute intermittent porphyria and erythropoietic protoporphyria. The molecular genetics of the porphyrias is very heterogenous. Nearly every family has its own mutation. The mutations identified account for the corresponding enzymatic deficiencies, which may remain clinically silent throughout life. Thus, the recognition of the overt disorder with extrahepatic manifestations depends on the demonstration of biochemical abnormalities due to these primary defects and compensatory hepatic overexpression of hepatic delta-aminolaevulinic acid synthase in the acute porphyrias. Consequently, haem precursors are synthesized in excess. The increased metabolites upstream of the enzymatic defect are excreted into urine and faeces. The diagnosis is based on their evaluation. Primary enzymatic or molecular analyses are noncontributary and may be misleading. Acute polysymptomatic exacerbations accompany a high excretory constellation of porphyrin precursors delta-aminolaevulinic acid and porphobilinogen. Homozygous or compound heterozygous variants of acute hepatic porphyrias may already manifest in childhood.

Hereditary coproporphyria in Germany: clinical-biochemical studies in 53 patients

OBJECTIVES

To describe the biochemical and clinical features in hereditary coproporphyria (HCP).

DESIGN AND METHOD

Within the last 20 years, we investigated 53 patients (male:female = 1:2.5; age = 8-86 years) suffering from HCP. We describe the characteristic levels of urine, and fecal porphyrins and their precursors in hereditary coproporphyria and present the clinical features. Especially, we measured the coproporphyrin isomers I and III.

RESULTS AND CONCLUSION

The group of hereditary coproporphyria patients exhibited a significantly higher (p<0.0001) excretion of urinary porphyrin precursors, delta-aminolevulinic acid (median = 84 micromol/24 h) and porphobilinogen (median = 39 micromol/24 h), as compared to controls (delta-aminolevulinic acid: 22 micromol/24 h, porphobilinogen: 3 micromol/24 h; median, n = 20). The median of coproporphyrin in urine (1315 nmol/24 h) and feces (1855 nmol/g) were enhanced 12- and 168-fold, as compared to healthy subjects (urinary coproporphyrin: 106 nmol/24 h, fecal coproporphyrin: 11 nmol/g; median, n = 20). During therapy on one female patient, with IV application of heme arginate, a considerable decline of porphyrin precursors and porphyrin excretion was observed. The examination of urinary and fecal coproporphyrin isomers I and III revealed an excessive elevation of the coproporphyrin isomer III of 87% in urine and 94% in feces, respectively (normal: urinary isomer III = 69-83% and fecal isomer III = 25-40%). In feces the increase of isomer III caused an inversion of the physiologic coproporphyrin isomer III:I ratio that could be recognized in all various stages in hereditary coproporphyria and in children. Acute attacks of hereditary coproporphyria are accompanied by an acute polysymptomatic clinical syndrome, and this is associated with high levels of urinary porphyrin precursors. On review of our patients, the highest percentage had abdominal pain (89%), followed by neurologic (33%), psychiatric (28%), cardiovascular (25%), and skin symptoms (14%).