Reducing diagnostic delays in acute hepatic porphyria using health records data and machine learning.

BACKGROUND: Acute hepatic porphyria (AHP) is a group of rare but treatable conditions associated with diagnostic delays of 15 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. We sought to train and characterize models for identifying patients with AHP. METHODS: This diagnostic study used structured and notes-based EHR data from 2 centers at the University of California, UCSF (2012-2022) and UCLA (2019-2022). The data were split into 2 cohorts (referral and diagnosis) and used to develop models that predict (1) who will be referred for testing of acute porphyria, among those who presented with abdominal pain (a cardinal symptom of AHP), and (2) who will test positive, among 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. The case cohort was 81% female 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. Our primary outcome was the 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: 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.

Elevated homocysteine is negatively correlated with plasma cystathionine ß-synthase activity in givosiran-treated patients.

Givosiran is a subcutaneously administered, liver-targeted RNA interference (RNAi) therapeutic that has been approved for treating acute hepatic porphyria (AHP). Elevation in plasma homocysteine (hyperhomocysteinemia) has been reported in AHP patients, and treatment with givosiran has been reported to further increase homocysteine levels in some patients. The mechanism of homocysteine elevation during givosiran treatment is unknown, but has been hypothesized to be mediated by a reduction in activity of cystathionine ß-synthase (CBS), which uses homocysteine as a substrate. A liquid chromatography-tandem mass spectrometry-based assay was adapted to measure circulating CBS activity. Using plasma collected from the Phase III ENVISION study, CBS activity was measured to directly evaluate whether it is associated with elevated homocysteine levels in givosiran-treated patients. CBS activity was reduced following givosiran treatment and both homocysteine and methionine levels were inversely correlated with CBS activity. Following administration of a supplement containing vitamin B6, a cofactor for CBS, in four patients during the trial, plasma CBS activity was found to increase, mirroring a corresponding decrease in homocysteine levels. These results support the hypothesis that elevated homocysteine levels following givosiran treatment result from a reduction of CBS activity and that vitamin B6 supplementation lowers homocysteine levels by increasing CBS activity.

Canadian guidance for diagnosis and management of acute hepatic porphyrias.

Acute hepatic porphyrias (AHP) comprise four rare monogenic autosomal conditions. Each is linked to a deficiency of heme metabolizing enzymes. Common manifestations include severe abdominal pain, nausea, confusion, hyponatremia, hypertension, tachycardia, and neuropathy. Diagnosis is challenging due to a non-specific, variable presentation with symptoms mimicking other common conditions. Initial diagnosis of AHP can be made with a test for urinary porphobilinogen, δ-aminolevulinic acid and porphyrins using a single random (spot) sample. However, many patients have complications due to delays in diagnosis and management. A novel small interfering RNA-based agent, givosiran, has demonstrated efficacy in reducing acute attacks in a recent Phase III trial, leading to its approval for the management of AHP. Early diagnosis is crucial for the timely introduction of disease-modifying treatments that reduce impairments, enhance quality of life, and extend survival. In this guidance, we aim to improve awareness and outcomes of AHP by making recommendations about diagnosis, monitoring, and treatment in Canada.

Update on heme biosynthesis, tissue-specific regulation, heme transport, relation to iron metabolism and cellular energy.

Heme is a primordial macrocycle upon which most aerobic life on Earth depends. It is essential to the survival and health of nearly all cells, functioning as a prosthetic group for oxygen-carrying proteins and enzymes involved in oxidation/reduction and electron transport reactions. Heme is essential for the function of numerous hemoproteins and has numerous other roles in the biochemistry of life. In mammals, heme is synthesised from glycine, succinyl-CoA, and ferrous iron in a series of eight steps. The first and normally rate-controlling step is catalysed by 5-aminolevulinate synthase (ALAS), which has two forms: ALAS1 is the housekeeping form with highly variable expression, depending upon the supply of the end-product heme, which acts to repress its activity; ALAS2 is the erythroid form, which is regulated chiefly by the adequacy of iron for erythroid haemoglobin synthesis. Abnormalities in the several enzymes of the heme synthetic pathway, most of which are inherited partial enzyme deficiencies, give rise to rare diseases called porphyrias. The existence and role of heme importers and exporters in mammals have been debated. Recent evidence established the presence of heme transporters. Such transporters are important for the transfer of heme from mitochondria, where the penultimate and ultimate steps of heme synthesis occur, and for the transfer of heme from cytoplasm to other cellular organelles. Several chaperones of heme and iron are known and important for cell health. Heme and iron, although promoters of oxidative stress and potentially toxic, are essential cofactors for cellular energy production and oxygenation.

[An overview of porphyrias]. / Porphyrien ­ eine Übersicht.

Porphyrias are predominantly genetic metabolic disorders caused by dysregulation of specific enzymes in porphyrin-heme biosynthesis. The enzymatic dysfunction leads to formation and excretion of intermediate metabolic products in the form of porphyrins and/or their precursors δ­aminolevulinic acid and porphobilinogen, which have cyto- and tissue-toxic properties. Clinically, porphyrias are extremely diverse, with symptoms ranging from skin changes on light-exposed areas of the body to potentially life-threatening neurovisceral attacks. Biochemical tests in urine, blood and stool are used for diagnosis, which can be supplemented by molecular genetic analyses. Treatment of the various forms of porphyria is complex and often requires close interdisciplinary cooperation between different medical specialties.

Practical recommendations for biochemical and genetic diagnosis of the porphyrias.

The porphyrias are a group of rare inborn errors of metabolism associated with various clinical presentations and long-term complications, making them relevant differential diagnoses to consider for many clinical specialities, especially hepatologists, gastroenterologists and dermatologists. To diagnose a patient with porphyria requires appropriate biochemical investigations, as clinical features alone are not specific enough. Furthermore, it is important to be aware that abnormalities of porphyrin accumulation and excretion occur in many other disorders that are collectively far more common than the porphyrias. In this review, we provide an overview of porphyria-related tests with their strengths and limitations, give recommendations on requesting and diagnostic approaches in non-expert and expert laboratories for different clinical scenarios and discuss the role of genetic testing in the porphyrias. To diagnose porphyria in a currently symptomatic patient requires analysis of biochemical markers to demonstrate typical patterns of haem precursors in urine, faeces and blood. The use of genomic sequencing in diagnostic pathways for porphyrias requires careful consideration, and the demonstration of increased porphyrin-related markers is necessary prior to genomic testing in symptomatic patients. In the acute porphyrias, genomic testing is presently a useful adjunct for genetic counselling of asymptomatic family members and the most common cutaneous porphyria, porphyria cutanea tarda, is usually a sporadic, non-hereditary disease. Getting a correct and timely porphyria diagnosis is essential for delivering appropriate care and ensuring best patient outcome.

Afamelanotide for Treatment of the Protoporphyrias: Impact on Quality of Life and Laboratory Parameters in a US Cohort.

BACKGROUND: Erythropoietic protoporphyria (EPP) and X-linked protoporphyria (XLP) are rare disorders of heme biosynthesis characterized by severe cutaneous phototoxicity. Afamelanotide, an α-melanocyte-stimulating hormone analogue, is the only approved treatment for protoporphyria and leads to increased light tolerance and improved quality of life (QoL). However, published experience with afamelanotide in the US is limited. METHODS: Here, we report on all adults who received at least one dose of afamelanotide at the Massachusetts General Hospital Porphyria Center from 2021 to 2022. Changes in the time to phototoxic symptom onset, QoL, and laboratory parameters were assessed before and during treatment with afamelanotide. RESULTS: A total of 29 patients with protoporphyria were included, 26 of whom (72.2%) received ≥2 afamelanotide implants. Among the patients who received ≥2 implants, the median time to symptom onset following sunlight exposure was 12.5 min (IQR, 5-20) prior to the initiation of afamelanotide and 120 min (IQR, 60-240) after treatment (p < 0.001). Improvements in QoL during afamelanotide treatment were measured using two QoL tools, with good correlation observed between these two instruments. Finally, we found no improvements in the median levels of metal-free erythrocyte protoporphyrin, plasma protoporphyrin, or liver biochemistries during versus prior to the initiation of afamelanotide treatment. CONCLUSIONS: This study highlights a dramatic clinical benefit of afamelanotide in relation to light tolerance and QoL in protoporphyria, albeit without improvement in protoporphyrin levels or measures of liver function.

Congenital erythropoietic porphyria.

Congenital erythropoietic porphyria (CEP) is a rare autosomal recessive disease due to the deficient, but not absent, activity of uroporphyrinogen III synthase (UROS), the fourth enzyme in the heme biosynthesis pathway. Biallelic variants in the UROS gene result in decreased UROS enzymatic activity and the accumulation of non-physiologic Type I porphyrins in cells and fluids. Overproduced uroporphyrins in haematopoietic cells are released into the circulation and distributed to tissues, inducing primarily hematologic and dermatologic symptoms. The clinical manifestations vary in severity ranging from non-immune hydrops fetalis in utero to mild dermatologic manifestations in adults. Here, the biochemical, molecular and clinical features of CEP as well as current and new treatment options, including the rescue of UROS enzyme activity by chaperones, are presented.

Neurofilament light chain as a biomarker for acute hepatic porphyrias.

Background: Acute hepatic porphyrias (AHP) represent a rare group of inherited metabolic disorders of heme biosynthesis pathway. This study aims to determine the diagnostic and prognostic value of serum neurofilament light chain (NfL) as potential biomarker for AHP. Methods: We conducted a cross-sectional observational study to evaluate NfL levels in patients with AHP. They were divided in different groups: normal health individuals; patients with definitive diagnosis of AHP during acute episodes; patients with AHP and infrequent attacks; patients with AHP and recurrent attacks; asymptomatic individuals with positive genetic testing and urinary delta-aminolevulinic acid (ALA) and porphobilinogen (PBG) levels elevated 4 or more times ("high excretors"); asymptomatic individuals with exclusive positive genetic test; control group with Hereditary Amyloidosis related to Transthyretin with Polyneuropathy (ATTRv-PN). Results: During acute attacks, serum NfL levels were 68 times higher compared to normal controls and disclosed a strong correlation with ALA and PBG levels; also exhibited elevated levels in patients with chronic symptoms regardless of the number of disease attacks compared to healthy controls, and at similar levels to patients with ATTRv-PN, which is a model of progressive neuropathy. Conclusion: This study represents the first to establish NfL as a biomarker for AHP, disclosing NfL as a sensitive biomarker for axonal damage and chronic symptom occurrence. This study not only underscores that neurological damage associated with the disease in any patient, irrespective of the number of attacks, but also reinforces the progressive and profoundly debilitating nature of acute and chronic symptoms observed in individuals with AHP.

Afamelanotide in protoporphyria and other skin diseases: a review.

Afamelanotide is a synthetic alpha melanocyte stimulating hormone presenting a higher activity than natural hormones. Its main properties are related to the enhanced production of eumelanin by agonistically binding to the melanocortin-1 receptor. Since 2016 afamelanotide has been especially applied to treat cases of erythropoietic porphyria (EPP), where painful photosensitivity has been observed since early childhood. The positive effect of afamelanotide in EPP administered subcutaneously improved tolerance to artificial white light and increased pain-free time spent in direct sunlight. In this review we summarize the possible use of afamelanotide in dermatology, with special emphasis on EPP and encourage including afamelanotide as a treatment option in patient care.

The clinical management of porphyria cutanea tarda: An update.

Porphyria cutanea tarda (PCT) is the commonest of the porphyrias (Semin Liver Dis 1998;18:67). It often occurs secondary to an underlying internal disorder, has significant impacts on liver health and longevity, and is a treatable disease. Thus, for the clinician, recognising the disease to make the correct diagnosis, identifying causative underlying diseases, and treating the porphyria and its complications, are crucial. Although reviews on the management of PCT have been written, there have recently been significant advances in the understanding of the factors predisposing to the disease, and of its wider health impacts. This review aims to help the clinician to diagnose and manage patients with PCT, with an emphasis on the impact of recent advances on clinical management.

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.

Neurodevelopmental disorder in a patient with HMBS and SCN3A variants-A possibly blended phenotype further delineating autosomal recessive HMBS related disease.

Monoallelic pathogenic HMBS variants are a well-established cause of acute intermittent porphyria (AIP), whereas biallelic pathogenic variants may cause HMBS-related leukoencephalopathy which remains a poorly characterized disorder. We describe an 8-year-old girl with hypotonia, hearing impairment, horizontal nystagmus, bilateral strabismus, impaired visual acuity, and optic nerve atrophy. She had no epilepsy but sleep electroencephalogram showed paroxysmal changes in the right hemisphere with secondary generalizations. Brain magnetic resonance imaging was unremarkable apart from a few small white matter hyperintensities. Exome sequencing (ES) initially prioritized a SCN3A c.3822G>A de novo variant whose sole causative role was eventually questioned as not fully compatible with symptoms. ES reanalysis revealed a homozygous c.674G>A HMBS variant. In the monoallelic form this variant is a known cause of AIP, whereas in trans with another HMBS pathogenic variant it was associated with the HMBS-related leukoencephalopathy in four individuals. Despite lack of signs/symptoms of porphyria, literature analysis suggested that HMBS c.674G>A likely contributed to the disease either as the sole cause or together with SCN3A c.3822G>A as a part of blended phenotype. Our report adds to the relatively small number of described cases of HMBS-related leukoencephalopathy and emphasizes that autosomal recessive form of HMBS disease can be present in the absence of porphyria symptoms.

Unveiling the Chameleon: A Case Report on Acute Intermittent Porphyria.

Acute intermittent porphyria (AIP) is a rare autosomal dominant metabolic disorder with low penetrance, often presenting with a broad spectrum of clinical manifestations. Acute neurovisceral attacks commonly occur in young women, mimicking signs and symptoms of other medical and psychiatric conditions, thus delaying the diagnosis. We present the case of an 18-year-old female college student with recurrent hospitalizations for intractable abdominal pain, now again with pain and new subjective hematuria. The patient had previously undergone an endoscopy/colonoscopy with negative biopsies and serologies for acute pathology, including celiac disease. Celiac studies were repeated, given the possibility of inadvertent gluten exposure before the onset of the latest symptoms, but were negative. Basic labs and repeat imaging, including contrast-enhanced CT, MRI, and magnetic resonance (MR) enterography of the abdomen, continued to be unremarkable, and the patient's symptoms were felt to be functional in etiology. The patient's urinalysis was normal, and pregnancy was also ruled out. The patient continued to have pain despite receiving opiate analgesics, thus prompting a psychiatry consultation. She was diagnosed with acute adjustment disorder with anxiety and was started on hydroxyzine. Due to persistent symptoms, serum and urine samples were sent, revealing low levels of porphobilinogen deaminase (PBGD) and hydroxymethylbilane synthase (HMBS) gene mutation, confirming the diagnosis of AIP. She was treated with oral glucose and outpatient IV hemin infusions with the resolution of symptoms. AIP presents a nonspecific and highly variable clinical picture, often making it a challenging diagnosis due to such a broad differential. While our patient was thought to have acute adjustment disorder due to an unremarkable initial workup, further testing revealed otherwise. This case demonstrates how clinicians must have a high suspicion of AIP when caring for young females, manifesting with neurovisceral and psychiatric signs and symptoms. Timely diagnosis improves a patient's quality of life and can decrease overutilization of healthcare resources.

Porphyria cutanea tarda in Scotland: underlying associations and treatment approaches.

BACKGROUND: Despite its rarity, porphyria cutanea tarda (PCT) is globally recognized as the most common form of cutaneous porphyria. This study aims to review the underlying associations and treatment of PCT in Scotland. METHODS: We retrospectively reviewed data on 27 patients diagnosed with PCT between 1987 and 2022 at the Scottish Cutaneous Porphyria Service. RESULTS: Males slightly predominated (66.7%). The mean ± standard deviation (SD) age at diagnosis was 55.6 ± 12.5 years. Common associated factors were heavy alcohol intake (88.5%), genetic hemochromatosis (72%), smoking (45.5%), and hepatitis C virus infection (16%). Most had multiple associated factors (70.4%). Patients with genetic hemochromatosis with the C282Y genotype exhibited higher median transferrin saturation (69.5 vs. 35, P = 0.004) and ferritin levels (observed in males only) (1175 vs. 339; P = 0.014) than those with the H636D genotype. Most (52%) received combination therapy of venesection and antimalarials, followed by venesection monotherapy (32%) and antimalarial monotherapy (16%). Overall, 95.2% achieved biochemical improvement. Median time to improvement was 7, 5, and 9 months with venesection, antimalarial, and combined treatments, respectively (P = 0.173). Biochemical remission was achieved in 50% of patients. Remission occurred in 2/4 of patients with antimalarial monotherapy (median time 19 months) and 9/13 patients with combined treatment (median time 26 months). Biochemical relapse was found in three patients, all of whom received combination therapy. CONCLUSION: Excess alcohol intake and genetic hemochromatosis were the most common underlying associations with PCT in our Scottish cohort. Treatment for PCT should be individualized, and long-term follow-up is needed to monitor for disease relapse.

CRISPR editing to mimic porphyria combined with light: A new preclinical approach for prostate cancer.

Thanks to its very high genome-editing efficiency, CRISPR-Cas9 technology could be a promising anticancer weapon. Clinical trials using CRISPR-Cas9 nuclease to ex vivo edit and alter immune cells are ongoing. However, to date, this strategy still has not been applied in clinical practice to directly target cancer cells. Targeting a canonical metabolic pathway essential to good functioning of cells without potential escape would represent an attractive strategy. We propose to mimic a genetic metabolic disorder in cancer cells to weaken cancer cells, independent of their genomic abnormalities. Mutations affecting the heme biosynthesis pathway are responsible for porphyria, and most of them are characterized by an accumulation of toxic photoreactive porphyrins. This study aimed to mimic porphyria by using CRISPR-Cas9 to inactivate UROS, leading to porphyrin accumulation in a prostate cancer model. Prostate cancer is the leading cancer in men and has a high mortality rate despite therapeutic progress, with a primary tumor accessible to light. By combining light with gene therapy, we obtained high efficiency in vitro and in vivo, with considerable improvement in the survival of mice. Finally, we achieved the preclinical proof-of-principle of performing cancer CRISPR gene therapy.