Laboratory Diagnosis of Porphyria

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.

Protoporphyrin IX in serum of high-grade glioma patients: A novel target for disease monitoring via liquid biopsy

High-grade gliomas (HGG) carry a dismal prognosis. Diagnosis comprises MRI followed by histopathological evaluation of tissue; no blood biomarker is available. Patients are subjected to serial MRIs and, if unclear, surgery for monitoring of tumor recurrence, which is laborious. MRI provides only limited diagnostic information regarding the differentiation of true tumor progression from therapy-associated side effects. 5-aminolevulinic acid (5-ALA) is routinely used for induction of protoporphyrin IX (PpIX) accumulation in malignant glioma tissue, enabling improved tumor visualization during fluorescence-guided resection (FGR). We investigated whether PpIX can also serve as a serum HGG marker to monitor relapse. Patients (HGG: n = 23 primary, pHGG; n = 5 recurrent, rHGG) undergoing FGR received 5-ALA following standard clinical procedure. The control group of eight healthy volunteers (HCTR) also received 5-ALA. Serum was collected before and repeatedly up to 72 h after drug administration. Significant PpIX accumulation in HGG was observed after 5-ALA administration (ANOVA: p = 0.005, post-hoc: HCTR vs. pHGG p = 0.029, HCTR vs. rHGG p = 0.006). Separation of HCTR from pHGG was possible when maximum serum PpIX levels were reached (CI95% of tMax). ROC analysis of serum PpIX within CI95% of tMax showed successful classification of HCTR and pHGG (AUCROC 0.943, CI95% 0.884-1.000, p < 0.001); the optimal cut-off for diagnosis was 1275 pmol PpIX/ml serum, reaching 87.0% accuracy, 90.5% positive predictive and 84.0% negative predictive value. Baseline PpIX level was similar in patient and control groups. Thus, 5-ALA is required for PpIX induction, which is safe at the standard clinical dosage. PpIX is a new target for liquid biopsy in glioma. More extensive clinical studies are required to characterize its full potential.

A case report of acute intermittent porphyria leading to severe disability

Acute intermittent porphyria (AIP) is a rare inherited metabolic disorder resulting from increased production of porphyrins and their precursors, δ-aminolevulinic acid (ALA) and porphobilinogen (PBG), due to deficiencies in the enzymatic activity of the heme synthesis pathway. The disease is typically characterized by a triad of abdominal pain, neurologic impairment symptoms, and psychiatric abnormalities. However, only a small percentage of patients present with this classic triad of symptoms. Our female patient, aged 23, was admitted to the hospital with a 4-year history of abnormal mood episodes and weakness in the limbs for over 1 week. She had a previous medical history of intestinal obstruction. After admission, a cranial MRI revealed reversible posterior leukoencephalopathy imaging manifestations, and the patient exhibited weakness of the extremities, respiratory failure, seizures, and severely reduced serum sodium concentration. The diagnosis of AIP was ultimately confirmed by a positive urine PBG-sunlight test and analysis of HMBS gene variants. The absence of typical triadic signs in acute attacks of AIP can make early recognition of the disease challenging. We present a case with multiple typical clinical manifestations of AIP in the hope of aiding clinicians in fully recognizing acute intermittent porphyria.

Portuguese Consensus on Acute Porphyrias: Diagnosis, Treatment, Monitoring and Patient Referral

Acute porphyrias are a group of rare genetic metabolic disorders, caused by a defect in one of the enzymes involved in the heme biosynthesis, which results in an abnormally high accumulation of toxic intermediates. Acute porphyrias are characterized by potentially life-threatening attacks and, for some patients, by chronic manifestations that negatively impact daily functioning and quality of life. Clinical manifestations include a nonspecific set of gastrointestinal, neuropsychiatric, and/or cutaneous symptoms. Effective diagnostic methods are widely available, but due to their clinical heterogeneity and non-specificity, many years often elapse from symptom onset to diagnosis of acute porphyrias, delaying the treatment and increasing morbidity. Therefore, increased awareness of acute porphyrias among healthcare professionals is paramount to reducing disease burden. Treatment of acute porphyrias is centered on eliminating the potential precipitants, symptomatic treatment, and suppressing the hepatic heme pathway, through the administration of hemin or givosiran. Moreover, properly monitoring patients with acute porphyrias and their relatives is fundamental to preventing acute attacks, hospitalization, and long-term complications. Considering this, a multidisciplinary panel elaborated a consensus paper, aiming to provide guidance for an efficient and timely diagnosis of acute porphyrias, and evidence-based recommendations for treating and monitoring patients and their families in Portugal. To this end, all authors exhaustively reviewed and discussed the current scientific evidence on acute porphyrias available in the literature, between November 2022 and May 2023.

Quantification of Urine and Plasma Porphyrin Precursors Using LC-MS in Acute Hepatic Porphyrias: Improvement in Routine Diagnosis and in the Monitoring of Kidney Failure Patients

BACKGROUND

The quantification of delta-aminolevulinic acid (ALA) and porphobilinogen (PBG) in urine are the first-line tests for diagnosis and monitoring of acute hepatic porphyrias (AHP). Ion-exchange chromatography (IEC), which is time- and staff-consuming and limited to urine, is still the preferred method in many specialized laboratories, despite the development of mass spectrometry-based methods.

METHODS

We describe a new LC-MS method that allows for rapid and simple quantification of ALA and PBG in urine and plasma with an affordable instrument that was used to analyze 2260 urine samples and 309 blood samples collected in 2 years of routine activity. The results were compared to those obtained with IEC, and urine reference ranges and concentrations in asymptomatic carriers were determined. Plasma concentrations were measured in healthy subjects and subgroups of symptomatic and asymptomatic AHP carriers.

RESULTS

In urine, the clinical decision limits were not impacted by the change of method despite discrepancies in low absolute concentrations, leading to lower normal values. Two-thirds of asymptomatic AHP carriers (with the exception of coproporphyria carriers) showed an increased urine PBG concentration. Urine and plasma levels showed a good correlation except in patients with kidney disease in whom the urine/plasma ratio was relatively low.

CONCLUSION

We described an LC-MS based method for the routine diagnosis and monitoring of AHP that allows for the detection of more asymptomatic carriers than the historical method. Blood analysis appears to be particularly relevant for patients with kidney disease, where urine measurement underestimates the increase in ALA and PBG levels.

Mitochondrial DNA Copy Number Drives the Penetrance of Acute Intermittent Porphyria

No published study has investigated the mitochondrial count in patients suffering from acute intermittent porphyria (AIP). In order to determine whether mitochondrial content can influence the pathogenesis of porphyria, we measured the mitochondrial DNA (mtDNA) copy number in the peripheral blood cells of 34 patients and 37 healthy individuals. We found that all AIP patients had a low number of mitochondria, likely as a result of a protective mechanism against an inherited heme synthesis deficiency. Furthermore, we identified a close correlation between disease penetrance and decreases in the mitochondrial content and serum levels of PERM1, a marker of mitochondrial biogenesis. In a healthy individual, mitochondrial count is usually modulated to fit its ability to respond to various environmental stressors and bioenergetic demands. In AIP patients, coincidentally, the phenotype only manifests in response to endogenous and exogenous triggers factors. Therefore, these new findings suggest that a deficiency in mitochondrial proliferation could affect the individual responsiveness to stimuli, providing a new explanation for the variability in the clinical manifestations of porphyria. However, the metabolic and/or genetic factors responsible for this impairment remain to be identified. In conclusion, both mtDNA copy number per cell and mitochondrial biogenesis seem to play a role in either inhibiting or promoting disease expression. They could serve as two novel biomarkers for porphyria.

Nutritional Interventions with Bacillus coagulans Improved Glucose Metabolism and Hyperinsulinemia in Mice with Acute Intermittent Porphyria

Acute intermittent porphyria (AIP) is a metabolic disorder caused by mutations in the porphobilinogen deaminase (PBGD) gene, encoding the third enzyme of the heme synthesis pathway. Although AIP is characterized by low clinical penetrance (~1% of PBGD mutation carriers), patients with clinically stable disease report chronic symptoms and frequently show insulin resistance. This study aimed to evaluate the beneficial impact of nutritional interventions on correct carbohydrate dysfunctions in a mouse model of AIP that reproduces insulin resistance and altered glucose metabolism. The addition of spores of Bacillus coagulans in drinking water for 12 weeks modified the gut microbiome composition in AIP mice, ameliorated glucose tolerance and hyperinsulinemia, and stimulated fat disposal in adipose tissue. Lipid breakdown may be mediated by muscles burning energy and heat dissipation by brown adipose tissue, resulting in a loss of fatty tissue and improved lean/fat tissue ratio. Probiotic supplementation also improved muscle glucose uptake, as measured using Positron Emission Tomography (PET) analysis. In conclusion, these data provide a proof of concept that probiotics, as a dietary intervention in AIP, induce relevant changes in intestinal bacteria composition and improve glucose uptake and muscular energy utilization. Probiotics may offer a safe, efficient, and cost-effective option to manage people with insulin resistance associated with AIP.

Circadian Genes Expression Patterns in Disorders Due to Enzyme Deficiencies in the Heme Biosynthetic Pathway

Heme is a member of the porphyrins family of cyclic tetrapyrroles and influences various cell processes and signalling pathways. Enzyme deficiencies in the heme biosynthetic pathway provoke rare human inherited metabolic diseases called porphyrias. Protein levels and activity of enzymes involved in the heme biosynthetic pathway and especially 5'-Aminolevulinate Synthase 1 are featured by 24-h rhythmic oscillations driven by the biological clock. Heme biosynthesis and circadian pathways intermingle with mutual modulatory roles. Notably, heme is a ligand of important cogs of the molecular clockwork, which upon heme binding recruit co-repressors and inhibit the transcription of numerous genes enriching metabolic pathways and encoding functional proteins bringing on crucial cell processes. Herein, we assessed mRNA levels of circadian genes in patients suffering from porphyrias and found several modifications of core clock genes and clock-controlled genes expression, associated with metabolic and electrolytic changes. Overall, our results show an altered expression of circadian genes accompanying heme biosynthesis disorders and confirm the need to deepen the knowledge of the mechanisms through which the alteration of the circadian clock circuitry could take part in determining signs and symptoms of porphyria patients and then again could represent a target for innovative therapeutic strategies.

Consideration of Acute Porphyria in an Emergency Department Patient: A Case Report and Discussion of Common Pitfalls

INTRODUCTION

Porphyria refers to a group of disorders associated with defects in heme synthesis. They can be associated with severely debilitating features, including abdominal pain, psychiatric symptoms, neurological defects, and cardiovascular irregularities. Although these diseases are rare, patients with attacks often do present to the emergency department (ED) where consideration of porphyria is generally not included in the differential.

CASE REPORT

Here, we examine a case of a 16-year-old male who presented to our ED for evaluation of recurring abdominal pain and auditory hallucinations in which porphyria was considered by the emergency physician.

DISCUSSION

Not considering acute porphyria in patients with recurring neurovisceral symptoms in the ED can lead to missed opportunities for diagnosing such pathologies.

Development and validation of diagnostic algorithms for the laboratory diagnosis of porphyrias

Porphyrias are rare metabolic disorders of the haem synthesis. They can present with acute neurovisceral attacks, cutaneous symptoms, or a combination of both. As they present with a wide variety of clinical symptoms, diagnosis is often delayed and correct interpretation of porphyria-related tests remains a challenge for many physicians. We developed and validated two algorithms for the laboratory diagnosis of porphyrias based on presenting symptoms. Based on a literature search and clinical/laboratory expertise, we developed algorithms for acute and cutaneous porphyrias. We validated these algorithms using all porphyria related laboratory test requests between January 1st 2000 and September 30th 2020 in UZ Leuven. In addition, we also evaluated our algorithm using samples from the European porphyria network (EPNET) external quality assessment scheme (2010-2021). Sensitivity of the algorithm for acute porphyria was 100.0% [74.9%-100.0%] (13 acute intermittent porphyria (AIP) and 1 variegate porphyria [VP]) with a specificity of 98.5% [91.0%-100.0%] (65 patients). Sensitivity of the algorithm for cutaneous porphyria was 100% [95.1%-100.0%] (7 VP, 59 porphyria cutanea tarda (PCT), 23 erythropoietic protoporphyria (EPP), 2 X-linked erythropoietic protoporphyria [XLEPP]) with a specificity of 93.9% [82.9%-98.5%]. There were no diagnostic samples of other types of porphyria. The algorithms correctly identified 18 of the 19 EPNET porphyria cases. One of the two hereditary coproporphyria cases was missed. The algorithms for acute and cutaneous porphyria showed high sensitivity and specificity and can be used to aid the clinician in correctly interpreting the laboratory findings of porphyria-related tests.

Case Report: Variegate porphyria disclosed by post-gastric bypass complications and causing predominant painful sensorimotor axonal peripheral neuropathy

Background and aims: Porphyrias constitute a group of rare genetic diseases due to various, mostly autosomal dominant mutations, causing enzymatic deficiency in heme biosynthesis. As a result, neurotoxic porphyrin precursors and light-sensitive porphyrins accumulate, while dysfunction in their targets determines the disease symptoms. Variegate porphyria (VP), one of the acute hepatic porphyrias, is caused by a protoporphyrinogen oxidase (PPOX) mutation. During acute attacks, among other factors, triggered by drugs, stressors, or fasting, an increase in urinary and fecal porphobilinogen (PBG), aminolevulinic acid (ALA), and porphyrins occurs, damaging the autonomous, peripheral, or central nervous system. The disease remains often latent or displays minimal symptoms usually overlooked, exposing undiagnosed patients to potentially serious complications in the presence of the aforementioned triggers.

Case report: This 46-year-old woman presented, some days after a bariatric surgery, with severe flaccid tetraparesis and neuropathic pain, initially misdiagnosed as a functional neurological disorder. The severe axonal sensorimotor polyneuropathy led to further investigations, disclosing high urinary porphobilinogen, ALA, and porphyrin levels due to a new PPOX mutation. Retrospectively, it appeared that the patient had had typical VP symptoms (abdominal pain, fragile skin, and dark urine episodes) for years prior to the surgery. Treated with carbohydrate load, neurorehabilitation, and analgesics, she slowly recovered to full mobility, with partial autonomy in her daily life activities, although fatigue and severe pain persisted, preventing her from returning to work.

Conclusion: This case documents gastric bypass surgery as a trigger of severe VP invalidating neurological symptoms and illustrates how the delayed diagnosis and post-interventional complications could have been prevented by screening for porphyria cardinal symptoms prior to the intervention. Likewise, this cost-effective screening should be performed before any treatment influencing the diet, which would dramatically improve the porphyria diagnosis rate and outcome.

Psychological Aspect and Quality of Life in Porphyrias: A Review

The World Health Organization (WHO) describes “health” as a state of physical, mental, and social well-being and not merely the absence of disease or infirmity. Therefore, a biopsychosocial approach should be considered as an integral part of patients’ management. In this review, we summarize the available data starting from 1986 on the biological, psychological, and social aspects of porphyrias in order to provide a useful tool for clinicians about the missing knowledge within this field. Porphyrias are a group of rare metabolic disorders affecting the heme biosynthetic pathway and can be categorized into hepatic and erythropoietic. Here, a total of 20 articles reporting the psychological and the quality of life (QoL) data of porphyria patients affected by acute hepatic porphyrias (AHPs), Porphyria Cutanea Tarda (PCT), and Erythropoietic Protoporphyria (EPP) were analyzed. These 13 articles include reported quantitative methods using questionnaires, while the reaming articles employed qualitative descriptive approaches through direct interviews with patients by psychology professionals. We conclude that the use of questionnaires limits the complete description of all areas of a patient’s life compared to a direct interview with specialists. However, only a combined use of these methods could be the best approach for the correct disorder management.

Microcytosis in Erythropoietic Protoporphyria

Partial deficiency of the last enzyme of the heme biosynthetic pathway, namely, ferrochelatase (FECH), is responsible for erythropoietic protoporphyria (EPP) in humans. This disorder is characterized by painful skin photosensitivity, due to excessive protoporphyrin IX (PPIX) production in erythrocytes. Although several papers report the presence of iron deficiency anemia in about 50% of EPP patients, there is still no a conclusive explanation of the why this occurs. In the present work, we explored hematological indices and iron status in 20 unrelated Italian EPP patients in order to propose a new hypothesis. Our data show that microcytosis is present in EPP patients also in the absence of anemia and iron deficiency with a link between PPIX accumulation and reduced MCV, probably indicating an indirect condition of heme deficiency. Patients studied had a downward shift of iron parameters due to increased hepcidin concentrations only in a state of repleted iron stores. Interestingly, hemoglobin synthesis was not limited by iron supply except in cases with further iron loss, in which concomitantly increased soluble transferrin (Tf) receptor (sTfR) levels were detected. The mechanisms involved in the iron uptake downregulation in EPP remain unclear, and the role of PPIX accumulation in microcytosis.

Iron in Porphyrias: Friend or Foe?

Iron is a trace element that is important for many vital processes, including oxygen transport, oxidative metabolism, cellular proliferation, and catalytic reactions. Iron supports these functions mainly as part of the heme molecule. Heme synthesis is an eight-step process which, when defective at the level of one of the eight enzymes involved, can cause the development of a group of diseases, either inherited or acquired, called porphyrias. Despite the strict link between iron and heme, the role of iron in the different types of porphyrias, particularly as a risk factor for disease development/progression or as a potential therapeutic target or molecule, is still being debated, since contrasting results have emerged from clinical observations, in vitro studies and animal models. In this review we aim to deepen such aspects by drawing attention to the current evidence on the role of iron in porphyrias and its potential implication. Testing for iron status and its metabolic pathways through blood tests, imaging techniques or genetic studies on patients affected by porphyrias can provide additional diagnostic and prognostic value to the clinical care, leading to a more tailored and effective management.

Recognized and Emerging Features of Erythropoietic and X-Linked Protoporphyria

Erythropoietic protoporphyria (EPP) and X-linked protoporphyria (XLP) are inherited disorders resulting from defects in two different enzymes of the heme biosynthetic pathway, i.e., ferrochelatase (FECH) and delta-aminolevulinic acid synthase-2 (ALAS2), respectively. The ubiquitous FECH catalyzes the insertion of iron into the protoporphyrin ring to generate the final product, heme. After hemoglobinization, FECH can utilize other metals like zinc to bind the remainder of the protoporphyrin molecules, leading to the formation of zinc protoporphyrin. Therefore, FECH deficiency in EPP limits the formation of both heme and zinc protoporphyrin molecules. The erythroid-specific ALAS2 catalyses the synthesis of delta-aminolevulinic acid (ALA), from the union of glycine and succinyl-coenzyme A, in the first step of the pathway in the erythron. In XLP, ALAS2 activity increases, resulting in the amplified formation of ALA, and iron becomes the rate-limiting factor for heme synthesis in the erythroid tissue. Both EPP and XLP lead to the systemic accumulation of protoporphyrin IX (PPIX) in blood, erythrocytes, and tissues causing the major symptom of cutaneous photosensitivity and several other less recognized signs that need to be considered. Although significant advances have been made in our understanding of EPP and XLP in recent years, a complete understanding of the factors governing the variability in clinical expression and the severity (progression) of the disease remains elusive. The present review provides an overview of both well-established facts and the latest findings regarding these rare diseases.

Two Novel Hydroxymethylbilane Synthase Splicing Mutations Predispose to Acute Intermittent Porphyria

Acute intermittent porphyria (AIP) is an autosomal dominant genetic disease caused by a lack or decrease in hydroxymethylbilane synthase (HMBS) activity. It is characterized by acute nerve and visceral attacks caused by factors in the process of heme synthesis. The penetrance rate of this disease is low, and the heterogeneity is strong. Here, we reported two novel HMBS mutations from two unrelated Chinese AIP patients and confirmed the pathogenicity of these two mutations. We found the HMBS c.760–771+2delCTGAGGCACCTGGTinsGCTGCATCGCTGAA and HMBS c.88-1G>C mutations by second-generation sequencing and Sanger sequencing. The in vitro expression analysis showed that these mutations caused abnormal HMBS mRNA splicing and premature termination or partial missing of HMBS protein. Homologous modeling analysis showed that the HMBS mutants lacked the amino acids which are crucial for the enzyme activity or the protein stability. Consistently, enzyme activity analysis confirmed that the HMBS mutants’ overexpression cells exhibited the reduced enzyme activity compared with the HMBS wildtype overexpression cells. Our study identified and confirmed two novel pathogenic HMBS mutations which will expand the molecular heterogeneity of AIP and provide further scientific basis for the clinical diagnosis of AIP.