Effectiveness and tolerability of givosiran for the management of acute hepatic porphyria: A monocenter real-life evaluation.

Acute hepatic porphyrias (AHPs) are a family of rare, autosomal, dominantly inherited conditions characterized by abnormalities in the production of heme. Advances in molecular engineering have provided new therapeutic possibilities for modifying the heme synthetic pathway in patients with porphyria. In particular, the RNA interference therapeutic givosiran was approved for the treatment of adults and adolescents with AHP aged >12 years based on the positive results of the phase III trial ENVISION. Despite the extended characterization of the activity of givosiran in clinical trials, reports on the long-term effects and effectiveness of the treatment in clinical practice are still scant. To fill this gap, this case series describes a monocentric Italian cohort of AHP patients treated with givosiran. Overall, our real-life experience supports the clinical evidence that long-term treatment with givosiran is well tolerated and able to provide sustained and continuous benefit to patients with acute intermittent porphyria, as reflected by the reduction in the frequency of attacks. In our series, givosiran treatment was also associated with improvement in assessments of quality of life, pain and fatigue.

Preventing hyperhomocysteinemia using vitamin B6 supplementation in Givosiran-treated acute intermittent porphyria: Highlights from a case report and brief literature review.

Acute hepatic porphyrias are inherited metabolic disorders of heme biosynthesis characterized by the accumulation of toxic intermediate metabolites responsible for disabling acute neurovisceral attacks. Givosiran is a newly approved siRNA-based treatment of acute hepatic porphyria targeting the first and rate-limiting δ-aminolevulinic acid synthase 1 (ALAS1) enzyme of heme biosynthetic pathway. We described a 72-year old patient who presented with severe inaugural neurological form of acute intermittent porphyria evolving for several years which made her eligible for givosiran administration. On initiation of treatment, the patient developed a major hyperhomocysteinemia (>400 µmol/L) which necessitated to discontinue the siRNA-based therapy. A thorough metabolic analysis in the patient suggests that hyperhomocysteinemia could be attributed to a functional deficiency of cystathionine ß-synthase (CBS) enzyme induced by givosiran. Long-term treatment with vitamin B6, a cofactor of CBS, allowed to normalize homocysteinemia while givosiran treatment was maintained. We review the recently published cases of hyperhomocysteinemia in acute hepatic porphyria and its exacerbation under givosiran therapy. We also discuss the benefits of vitamin B6 supplementation in the light of hypothetic pathophysiological mechanisms responsible for hyperhomocysteinemia in these patients. Our results confirmed the importance of monitoring homocysteine metabolism and vitamin status in patients with acute intermittent porphyria in order to improve management by appropriate vitamin supplementation during givosiran treatment.

Xenobiotics Triggering Acute Intermittent Porphyria and Their Effect on Mouse Brain Respiratory Complexes.

Heme enzyme dysfunction causes a group of diseases called porphyrias. Particularly, a decrease in porphobilinogen deaminase, involved in the third step of heme biosynthesis, leads to acute intermittent porphyria (AIP). Considering our previous works demonstrating the multiplicity of brain metabolisms affected by porphyrinogenic agents, this study aimed to elucidate whether they cause any alteration on the mitochondrial respiratory chain. The activities of respiratory chain complexes (I to IV) were measured in encephalon mitochondria of CF1 male mice receiving volatile anesthetics: isoflurane (2 mL/kg) and sevoflurane (1.5 mL/kg), ethanol (30%), allylisopropylacetamide (AIA) (350 mg/kg), and barbital (167 mg/kg). Moreover, they were compared versus animals with pathological levels of 5-aminolevulinic acid (ALA, 40 mg/kg). Complex I-III activity was induced by isoflurane and decreased by AIA, ethanol, and ALA. Complex II-III activity was increased by sevoflurane and decreased by isoflurane and AIA. Complex II activity was increased by sevoflurane and barbital and decreased by AIA, ethanol, and ALA. Complex IV activity was increased by barbital and ALA and decreased by sevoflurane. The damage to the respiratory chain by ALA could be reflecting the pathophysiological condition of patients with AIP. Better understanding the broad effect of porphyrinogenic drugs and the mechanisms acting on the onset of AIP is vital in translational medicine.

Obstacles to Early Diagnosis of Acute Hepatic Porphyria: Current Perspectives on Improving Early Diagnosis and Clinical Management.

Porphyrias are, for the most part, inherited disorders of the heme biosynthetic pathway which lead to accumulation of specific intermediates responsible for most of the symptoms and signs of biochemically active disease. Acute hepatic porphyrias usually come to clinical attention primarily in women in their reproductive years who present with episodic, severe, generalized abdominal pain. Such acute attacks may also be associated with tachycardia, systemic arterial hypertension, hyponatremia, recent history of dark reddish to brownish urine, and anxiety, delirium, and sensory or motor neuropathies. Diagnosing AHPs is often challenging, requiring a high index of suspicion and the appropriate testing showing elevated ALA and/or PBG in a random urine specimen. Obstacles to diagnosis include inappropriate testing for porphyrins only, inadequate sample handling, and ordering genetic testing as the initial diagnostic test. While some of these pitfalls in diagnosis are surmountable with current knowledge, others are in need of more research.

One ring closer to a closure: the crystal structure of the ES3 hydroxymethylbilane synthase intermediate.

Hydroxymethylbilane synthase (HMBS), involved in haem biosynthesis, catalyses the head-to-tail coupling of four porphobilinogens (PBGs) via a dipyrromethane (DPM) cofactor. DPM is composed of two PBGs, and a hexapyrrole is built before the tetrapyrrolic 1-hydroxymethylbilane product is released. During this elongation, stable enzyme (E) intermediates are formed from the holoenzyme, with additional PBG substrates (S): ES, ES2 , ES3 and ES4 . Native PAGE and mass spectrometry of the acute intermittent porphyria (AIP)-associated HMBS variant p.Arg167Gln demonstrated an increased amount of ES3 . Kinetic parameters indicated catalytic dysfunction, however, the product release was not entirely prevented. Isolation and crystal structure analysis of the ES3 intermediate (PDB: 8PND) showed that a pentapyrrole was fully retained within the active site, revealing that polypyrrole elongation proceeds within the active site via a third interaction site, intermediate pyrrole site 3 (IPS3). The AIP-associated HMBS variant p.Arg195Cys, located on the opposite side to p.Arg167Gln in the active site, accumulated the ES4 intermediate in the presence of excess PBG, implying that product hydrolysis was obstructed. Arg167 is thus involved in all elongation steps and is a determinant for the rate of enzyme catalysis, whereas Arg195 is important for releasing the product. Moreover, by substituting residues in the vicinity of IPS3, our results indicate that a fully retained hexapyrrole could be hydrolysed in a novel site in proximity of the IPS3.

Update on the Porphyrias.

The porphyrias are a group of rare diseases, each resulting from a defect in a different enzymatic step of the heme biosynthetic pathway. They can be broadly divided into two categories, hepatic and erythropoietic porphyrias, depending on the primary site of accumulation of heme intermediates. These disorders are multisystemic with variable symptoms that can be encountered by physicians in any specialty. Here, we review the porphyrias and describe their clinical presentation, diagnosis, and management. We discuss novel therapies that are approved or in development. Early diagnosis is key for the appropriate management and prevention of long-term complications in these rare disorders.

Acute Intermittent Porphyria Labeled Initially As Guillain-Barre Syndrome: Challenging Diagnosis.

Acute intermittent porphyria (AIP) is an autosomal, dominant, rare metabolic disturbance that results from a defect in the activity of the heme biosynthesis. It has a heterogeneous presentation, making a prompt diagnosis challenging. We report a case of acute intermittent porphyria in a young female who underwent in vitro fertilization (IVF) and presented with recurrent abdominal pain and posterior reversible encephalopathy syndrome (PRES), progressing to acute progressive quadriparesis post-delivery.

Molecular analysis of eight splicing variants in the hydroxymethylbilane synthase gene.

Background: Molecular genetic testing is the most sensitive and specific method to confirm acute intermittent porphyria (AIP), a rare autosomal dominant disease, caused by Hydroxymethylbilane synthase (HMBS) gene mutation. According to the Human Gene Mutation Database (HGMD), approximately 20% of the reported HMBS gene variants affect pre-RNA splicing. Thus, the ensuing challenge is how to decipher the pathogenicity of these splicing variants. Methods: Using next-generation sequencing, we identified a novel heterozygous variant in the HMBS gene (c.160 + 5G>C) from a Chinese family with AIP. And, previously, seven HMBS variants (c.33 + 5G>A, c.88-16_88-4del, c.88-2A>G, c.161-1G>C, c.652-1G>A, c.772-2A>G and c.772-1G>C) have been reported to be linked with AIP. Herein, we performed a valid and novel in vitro minigene assay to analyze the pathogenicity of these eight splicing variants. Results: By minigene assay in 293 T cell experiments, we demonstrated that all eight variants caused splicing defects in the pre-mRNA of the HMBS gene: c.160 + 5G>C (intron3p_141bp retention), c.33 + 5G>C(intron1p_91bp retention), c.88-16_88-4del and c.88-2A>G (Exon3p_15bp deletion), c.161-1G>C (Exon4p_18bp deletion), c.652-1G>A (Exon11p_1bp deletion), c.772-2A>G and c.772-1G>C (intron11q_104bp retention or Exon12p_4bp deletion).Encouragingly, the c.160 + 5G>C RNA sequencing from peripheral blood lymphocytes was consistent with the minigene assay result. Conclusion: We have made a pioneering attempt to apply minigene in vitro validation to the HMBS gene to evaluate the splicing effect of eight variants, including a novel splice variant (c.160 + 5G>C). This study provides a molecular basis for future research on the pathogenesis and gene therapy of AIP.

Clinical feature and genetic analysis of HMBS gene in Chinese patients with acute intermittent porphyria: a systematic review.

Background: Early detection and diagnosis are important crucial to prevent life-threatening acute attacks in patients with acute intermittent porphyria (AIP). We aim to provide comprehensive data on the clinical and hydroxymethylbilane synthase (HMBS) gene variant characteristics and genotype-phenotype association of Chinese patients with AIP in order to improve clinicians' knowledge of AIP and reduce misdiagnosis and mistaken treatment. Methods: We searched the literature on Chinese patients with AIP in PubMed, Web of Science, Wiley Online Library, ScienceDirect and Chinese literature databases up to August 2023 in our analysis to explore the clinical and HMBS gene variant characteristics of Chinese patients with AIP. Results: A total of 41 original articles associated with Chinese AIP patients were included for analysis: 97 variants were detected in 160 unrelated families, including 35 missense, 29 frameshift, 24 splicing and 9 nonsense variants, with c.517C>T being the most common variant. Clinical data were reported in 77 of 160 patients: Most of them were female (67/77) and the age was 28.8 ± 9.9 years. The most common symptom was abdominal pain (73/77, 94.8%), followed by central nervous system symptoms (45/77, 58.4%). 13.0% (10/77) of patients experienced psychiatric symptoms. Hyponatremia was the most common electrolyte abnormality (42/77). 31 patients received carbohydrate loading therapy, and 30 of them were improved. 6 patients were treated with carbohydrate loading combined with hemin therapy and 5 eventually improved. All variants causing premature stop codons, frameshifts or enzyme activity center may experience more severe clinical phenotypes such as seizures, respiratory paralysis, intracranial hemorrhage disorder or respiratory failure. Conclusion: The most common presenting symptom in Chinese AIP patients was abdominal pain, followed by central nervous system symptoms. The HMBS gene analysis in Chinese AIP patients revealed that the heterogeneity is strong and the most common variant was missense mutation, with c.517C>T being the most common variant. The genotype-phenotype association helps guide clinical diagnosis and treatment. However, the treatment for AIP in China is limited and monolithic, and more attention needs to be paid to the treatment.

A novel mutation c.457C > T p.Q153 in the HMBS gene in a Mexican woman with acute intermittent porphyria.

Key Clinical Message: The detection of a novel HMBS gene mutation (c.457C > T) in a Mexican woman with acute intermittent porphyria underscores the importance of expanding genetic analyses in diverse populations to improve diagnosis, management, and knowledge of the disease's clinical implications. Abstract: Acute intermittent porphyria (AIP) is an autosomal dominant disorder caused by a deficiency in the enzymatic activity of porphobilinogen deaminase (HMBS), resulting in the accumulation of toxic heme metabolites. In this report, we present the case of a Mexican woman with AIP who experienced recurrent episodes of severe abdominal pain, weakness, vomiting, and insomnia. Despite the challenges in diagnosis and treatment, genetic analysis revealed a novel HMBS mutation, c.457C > T (p.Q153X), located in exon 9. This mutation induces a premature translational stop codon and had not been previously reported in medical literature among individuals with AIP. Remarkably, the patient exhibited a positive response to RNA interference therapy. We hypothesize that this novel HMBS mutation may potentially account for the more severe clinical presentation observed in this case. However, further research is necessary to establish a definitive link between this specific mutation and disease severity. The prevalence and genetic variants of AIP in Mexico remain largely unknown, underscoring the importance of conducting additional research and expanding genetic analyses to gain a better understanding of the clinical implications associated with these mutations.

Acute Porphyria: An Unusual Case Of Quadriparesis, Hypertension, Recurrent Severe Cyclic Abdominal Pain, And Seizures.

Porphyria refers to a rare group of genetically inherited or acquired disorders that arise due to reduced metabolic activity of any of the enzymes in the haem biosynthetic pathway. Defect in any enzyme causes the presentation of symptoms of porphyria. The epidemiology of Acute Intermittent Porphyria (AIP) is complicated because of its rarity and delay in diagnosis. We present the case of a seven-year-old girl who presented with multisystem involvement; her symptoms were quadriparesis, hypertension, recurrent severe cyclic abdominal pain, and seizures. These symptoms together were not explained by the differentials taken into account. She presented before puberty with no family history of such conditions, while being born of consanguineous marriage. Her symptoms along with urinary porphobilinogen positivity test helped to reach the diagnosis of AIP in the absence of cutaneous manifestations. This case highlights the variable presentation of porphyria and emphasises the importance of appropriate and timely diagnosis and management in these patients.

An Analysis and Literature Review of a Family Case of Acute Intermittent Porphyria With Initial Symptoms of Epileptic Seizure.

Acute intermittent porphyria (AIP) is the most common form of acute porphyria and is characterized by acute onset and recurrent episodes. Clinical presentation frequently initiates with gastrointestinal symptoms and is often misdiagnosed or delayed secondary to nonspecific symptoms. Acute porphyria with epilepsy as the primary symptom is a very unusual or unexpected manifestation. This family case found an unexpected association between acute porphyria and seizures. This patient is a 33-year-old woman whose initial symptom was symptomatic epilepsy, followed by significant abdominal pain. After excluding infection, immunity, and other factors, whole exome sequencing analysis showed the presence of c.22dupG mutation in the HMBS gene and the patient was finally diagnosed with AIP. Her symptoms significantly improved after receiving high-glucose and high-carbohydrate load treatment. This case report is rare and suggests that for patients who experience epileptic seizures coupled with complaints related to the abdomen, the possibility of porphyria should be specially considered in the differential diagnosis.

Needle in a Haystack: Acute Intermittent Porphyria, an Often-missed Differential Diagnosis of Abdominal Pain.

Acute intermittent porphyria (AIP) is a rare disease that arises due to deficiency of the biosynthetic enzyme porphobilinogen deaminase (PBGD) involved in heme synthesis. Acute attacks can present with abdominal pain and neurological symptoms, although vague in nature. Recurrent hospitalizations for idiopathic intermittent abdominal pain should warrant investigation for AIP. Posterior reversible encephalopathy (PRES) presents with visual disturbances and seizure-like activity and can be, although rarely, associated with AIP. It is noteworthy to know that antiepileptic medication used in management of PRES can in turn worsen AIP.

First Report of a Low-Frequency Mosaic Mutation in the Hydroxymethylbilane Synthase Gene Causing Acute Intermittent Porphyria.

Acute porphyrias are a group of monogenetic inborn errors of heme biosynthesis, characterized by acute and potentially life-threatening neurovisceral attacks upon exposure to certain triggering factors. Biochemical analyses can determine the type of acute porphyria, and subsequent genetic analysis allows for the identification of pathogenic variants in the specific gene, which provides information for family counselling. In 2017, a male Swiss patient was diagnosed with an acute porphyria while suffering from an acute attack. The pattern of porphyrin metabolite excretion in urine, faeces, and plasma was typical for an acute intermittent porphyria (AIP), which is caused by inherited autosomal dominant mutations in the gene for hydroxymethylbilane synthase (HMBS), the third enzyme in the heme biosynthetic pathway. However, the measurement of HMBS enzymatic activity in the erythrocytes was within the normal range and Sanger sequencing of the HMBS gene failed to detect any pathogenic variants. To explore the molecular basis of the apparent AIP in this patient, we performed third-generation long-read single-molecule sequencing (nanopore sequencing) on a PCR product spanning the entire HMBS gene, including the intronic sequences. We identified a known pathogenic variant, c.77G>A, p.(Arg26His), in exon 3 at an allelic frequency of ~22% in the patient's blood. The absence of the pathogenic variant in the DNA of the parents and the results of additional confirmatory studies supported the presence of a de novo mosaic mutation. To our knowledge, such a mutation has not been previously described in any acute porphyria. Therefore, de novo mosaic mutations should be considered as potential causes of acute porphyrias when no pathogenic genetic variant can be identified through routine molecular diagnostics.

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.

Acute Intermittent Porphyria: A Review and Rehabilitation Perspective.

Acute intermittent porphyria (AIP) is an uncommon metabolic disease that impacts multiple organs and can manifest in many ways. It is often misdiagnosed due to its nonspecific symptoms. Neurovisceral signs and symptoms should alert physicians to consider AIP in the differential after excluding more common causes. Identifying the underlying cause is critical in preventing acute attacks, and trigger avoidance is the optimal approach to managing AIP. Medications that are contraindicated should be reviewed thoroughly. Prompt intravenous hematin administration is the primary treatment for acute attacks, and additional pharmacological therapies may be necessary to treat concurrent symptoms. A severe neurological manifestation of AIP is flaccid paralysis or severe motor weakness, which can develop into total quadriplegia and respiratory insufficiency. A comprehensive rehabilitation program is an integral aspect of the treatment plan. Since the incidence of this disease is low, functional prognosis is not well-known. As a result, it is challenging to determine the most appropriate structure, intensity, and duration of rehabilitation therapy. By extending the treatment plan, individuals with tetraplegia due to AIP can continue to make functional gains years after the onset of weakness. Understanding the disease's functional prognosis will aid in coordinating resources and improving healthcare expenditures.

Reducing diagnostic delays in Acute Hepatic Porphyria using electronic health records data and machine learning: a multicenter development and validation study.

Importance: Acute Hepatic Porphyria (AHP) is a group of rare but treatable conditions associated with diagnostic delays of fifteen years on average. The advent of electronic health records (EHR) data and machine learning (ML) may improve the timely recognition of rare diseases like AHP. However, prediction models can be difficult to train given the limited case numbers, unstructured EHR data, and selection biases intrinsic to healthcare delivery. Objective: To train and characterize models for identifying patients with AHP. Design Setting and Participants: This diagnostic study used structured and notes-based EHR data from two centers at the University of California, UCSF (2012-2022) and UCLA (2019-2022). The data were split into two cohorts (referral, diagnosis) and used to develop models that predict: 1) who will be referred for testing of acute porphyria, amongst those who presented with abdominal pain (a cardinal symptom of AHP), and 2) who will test positive, amongst those referred. The referral cohort consisted of 747 patients referred for testing and 99,849 contemporaneous patients who were not. The diagnosis cohort consisted of 72 confirmed AHP cases and 347 patients who tested negative. Cases were female predominant and 6-75 years old at the time of diagnosis. Candidate models used a range of architectures. Feature selection was semi-automated and incorporated publicly available data from knowledge graphs. Main Outcomes and Measures: F-score on an outcome-stratified test set. Results: The best center-specific referral models achieved an F-score of 86-91%. The best diagnosis model achieved an F-score of 92%. To further test our model, we contacted 372 current patients who lack an AHP diagnosis but were predicted by our models as potentially having it (≥ 10% probability of referral, ≥ 50% of testing positive). However, we were only able to recruit 10 of these patients for biochemical testing, all of whom were negative. Nonetheless, post hoc evaluations suggested that these models could identify 71% of cases earlier than their diagnosis date, saving 1.2 years. Conclusions and Relevance: ML can reduce diagnostic delays in AHP and other rare diseases. Robust recruitment strategies and multicenter coordination will be needed to validate these models before they can be deployed.