Molecular mechanisms and clinical manifestations of hereditary hemorrhagic telangiectasia.

INTRODUCTION: Hereditary Hemorrhagic Telangiectasia (HHT) is charactered by telangiectasia and arteriovenous malformations (AVMs). Recurrent visceral and mucocutaneous bleeding is frequently reported among HHT patients, while data on the prevalence of thrombosis remains limited. This study aims to describe the clinical manifestations and molecular biological characteristics of HHT patients. METHODS: We conducted a retrospective study at Ruijin Hospital, affiliated with Shanghai Jiao Tong University School of Medicine. A total of 24 HHT patients, observed between January 2019 and December 2023, were included. We recorded the biological, clinical, and therapeutic events, with particular attention to bleeding and thrombotic events. Gene mutation analysis and blood constituent measurements were performed. RESULTS: The prevalence of bleeding among all HHT patients was 100 %, while thrombotic events were noted in 41.70 % of cases. Hepatic arteriovenous malformations (HAVMs) were identified in six patients, pulmonary arteriovenous malformations (PAVMs) in five patients, and cerebral arteriovenous malformations (CAVMs) in one patient. For patients with thrombosis, the discontinuation rates were 23.08 % for antiplatelet therapy and 33.33 % for anticoagulant therapy due to the increased risk of bleeding. Genetic mutations related to HHT were present in 16 patients, with ACVRL1 (activin A receptor-like type 1) mutations being the most frequent at 41.67 %, followed by ENG (endoglin) mutations at 20.83 %, and GDF2 (growth differentiation factor 2) mutations at 4.17 %. The incidence of PAVMs was 75.00 % in HHT1 patients with ENG mutations and 20 % in HHT2 patients with ACVRL1 mutations, while HAVMs occurred in 0 % and 40.00 % of these groups, respectively. Patients were divided into non-AVMs and AVMs groups. Compared to normal controls, von Willebrand factor (vWF) activity was significantly increased in all HHT patients (149.10 % vs. 90.65 %, P < 0.001). In the non-AVMs group, the median level of stromal cell-derived factor-1 (SDF-1) was significantly elevated (124.31 pg/mL vs. 2413.57 pg/mL, P < 0.05), while vWF antigen levels were markedly higher in the AVMs group (165.30 % vs. 130.60 %, P = 0.021). Further grouping of HHT patients based on bleeding and thrombosis phenotypes revealed that those with thrombosis had significantly higher median percentages of schistocytes (3.50 % vs. 0 %, P = 0.002), ferritin concentrations (318.50 µg/L vs. 115.50 µg/L, P = 0.001), and lactate dehydrogenase (LDH) levels (437 U/L vs. 105 U/L, P < 0.001). There were no significant differences in the activity of vWF, protein C (PC), protein S (PS), and factor VIII (FVIII) between the two groups. CONCLUSION: This study highlighted the complex relationship between arteriovenous malformations and genetic mutations in HHT patients. A comprehensive assessment of bleeding and thrombosis risks should be conducted for each HHT patient, additionally, further clinical studies are needed to explore the risk factors for thrombosis and anticoagulant-related bleeding in HHT.

A Microphysiological HHT-on-a-Chip Platform Recapitulates Patient Vascular Lesions.

Hereditary Hemorrhagic Telangiectasia (HHT) is a rare congenital disease in which fragile vascular malformations (VM) - including small telangiectasias and large arteriovenous malformations (AVMs) - focally develop in multiple organs. There are few treatment options and no cure for HHT. Most HHT patients are heterozygous for loss-of-function mutations affecting Endoglin (ENG) or Alk1 (ACVRL1); however, why loss of these genes manifests as VMs remains poorly understood. To complement ongoing work in animal models, we have developed a fully human, cell-based microphysiological model based on our Vascularized Micro-organ (VMO) platform (the HHT-VMO) that recapitulates HHT patient VMs. Using inducible ACVRL1 -knockdown, we control timing and extent of endogenous Alk1 expression in primary human endothelial cells (EC). Resulting HHT-VMO VMs develop over several days. Interestingly, in chimera experiments AVM-like lesions can be comprised of both Alk1-intact and Alk1-deficient EC, suggesting possible cell non-autonomous effects. Single cell RNA sequencing data are consistent with microvessel pruning/regression as contributing to AVM formation, while loss of PDGFB implicates mural cell recruitment. Finally, lesion formation is blocked by the VEGFR inhibitor pazopanib, mirroring positive effects of this drug in patients. In summary, we have developed a novel HHT-on-a-chip model that faithfully reproduces HHT patient lesions and that can be used to better understand HHT disease biology and identify potential new HHT drugs.

Hereditary Hemorrhagic Telangiectasia with Recurrent Epistaxis, Telangiectasia, Hepatic Arteriovenous Malformation, and a Poorly Developed Middle Cerebral Artery in a Patient with a Novel Mutation in the ACVRL1 Gene.

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal-dominant vascular disorder characterized by intractable epistaxis, mucocutaneous telangiectasias, and arteriovenous malformations (AVMs) in multiple organs, including the lungs, liver, gastrointestinal tract, brain, and spinal cord. We herein report a 50-year-old Japanese man with HHT who experienced recurrent epistaxis, telangiectasia in the cornea, apex of the tongue and fingers; hepatic AVM; and a poorly developed main arterial trunk in the right middle cerebral artery. A genetic analysis revealed a novel heterozygous mutation in the activin A receptor-like type 1 gene, with a frameshift mutation in NM_000020.3:c.826_836del (p.Ile276ProfsTer112).

Evaluation of Aav Capsids and Delivery Approaches for Hereditary Hemorrhagic Telangiectasia Gene Therapy.

Nosebleeds and intracranial hemorrhage from brain arteriovenous malformations (bAVMs) are among the most devastating symptoms of patients with hereditary hemorrhagic telangiectasis (HHT). All available managements have limitations. We showed that intravenous delivery of soluble FMS-related tyrosine kinase 1 using an adeno-associated viral vector (AAV9-sFLT1) reduced bAVM severity of endoglin deficient mice. However, minor liver inflammation and growth arrest in young mice were observed. To identify AAV variants and delivery methods that can best transduce brain and nasal tissue with an optimal transduction profile, we compared 3 engineered AAV capsids (AAV.cc47, AAV.cc84 and AAV1RX) with AAV9. A single-stranded CBA promoter driven tdTomato transgene was packaged in these capsids and delivered intravenously (i.v.) or intranasally (i.n.) to wild-type mice. A CMV promoter driven Alk1 transgene was packaged into AAV.cc84 and delivered to PdgfbiCre;Alk1 f/f mice through i.v. injection followed by brain AVM induction. Transduced cells in different organs, vessel density and abnormal vessels in the bAVMs, and liver inflammation were analyzed histologically. Liver and kidney function were measured enzymatically. Compared to other viral vectors, AAV.cc84, after i.v. delivery, transduced a high percentage of brain ECs and few hepatocytes; whereas after i.n. delivery, AAV.cc84 transduced ECs and perivascular cells in the brain, and ECs, epithelial cells, and skeletal muscles in the nose with minimum hepatocyte transduction. No changes to liver or kidney function were detected. Delivery of AAV.cc84-Alk1 through i.v. to PdgfbiCre;Alk1 f/f mice reduced bAVM severity. In summary, we propose that AAV.cc84-Alk1 is a promising candidate for developing gene therapy in HHT patients.

Evaluation of AAV Capsids and Delivery Approaches for Hereditary Hemorrhagic Telangiectasia Gene Therapy.

Nosebleeds and intracranial hemorrhage from brain arteriovenous malformations (bAVMs) are among the most devastating symptoms of patients with hereditary hemorrhagic telangiectasis (HHT). All available managements have limitations. We showed that intravenous (i.v.) delivery of soluble Feline McDonough Sarcoma (FMS)-related tyrosine kinase 1 using an adeno-associated viral vector (AAV9-sFLT1) reduced bAVM severity of endoglin deficient mice. However, minor liver inflammation and growth arrest in young mice were observed. To identify AAV variants and delivery methods that can best transduce brain and nasal tissue with an optimal transduction profile, we compared 3 engineered AAV capsids (AAV.cc47, AAV.cc84, and AAV1RX) with AAV9. A single-stranded CBA promoter driven tdTomato transgene was packaged in these capsids and delivered i.v. or intranasally (i.n.) to wild-type mice. A CMV promoter driven Alk1 transgene was packaged into AAV.cc84 and delivered to PdgfbiCre;Alk1f/f mice through i.v. followed by bAVM induction. Transduced cells in organs, vessel density, abnormal vessels in the bAVMs, and liver inflammation were analyzed histologically. Liver and kidney function were measured enzymatically. Compared to other viral vectors, AAV.cc84, after i.v. delivery, transduced a high percentage of brain endothelial cells (ECs) and few hepatocytes; whereas after i.n. delivery, AAV.cc84 transduced ECs and perivascular cells in the brain, and ECs, epithelial cells, and muscles in the nose with minimum hepatocyte transduction. No changes to liver or kidney function were detected. The delivery of AAV.cc84-Alk1 through i.v. to PdgfbiCre;Alk1f/f mice reduced bAVM severity. In summary, we propose that AAV.cc84-Alk1 is a promising candidate for developing gene therapy in HHT patients.

Investigation of the Genetic Determinants of Telangiectasia and Solid Organ Arteriovenous Malformation Formation in Hereditary Hemorrhagic Telangiectasia (HHT).

Telangiectases and arteriovenous malformations (AVMs) are the characteristic lesions of Hereditary Hemorrhagic Telangiectasia (HHT). Somatic second-hit loss-of-function variations in the HHT causative genes, ENG and ACVRL1, have been described in dermal telangiectasias. It is unclear if somatic second-hit mutations also cause the formation of AVMs and nasal telangiectasias in HHT. To investigate the genetic mechanism of AVM formation in HHT, we evaluated multiple affected tissues from fourteen individuals. DNA was extracted from fresh/frozen tissue of 15 nasal telangiectasia, 4 dermal telangiectasia, and 9 normal control tissue biopsies, from nine unrelated individuals with HHT. DNA from six formalin-fixed paraffin-embedded (FFPE) AVM tissues (brain, lung, liver, and gallbladder) from five individuals was evaluated. A 736 vascular malformation and cancer gene next-generation sequencing (NGS) panel was used to evaluate these tissues down to 1% somatic mosaicism. Somatic second-hit mutations were identified in three in four AVM biopsies (75%) or half of the FFPE (50%) samples, including the loss of heterozygosity in ENG in one brain AVM sample, in which the germline mutation occurred in a different allele than a nearby somatic mutation (both are loss-of-function mutations). Eight of nine (88.9%) patients in whom telangiectasia tissues were evaluated had a somatic mutation ranging from 0.68 to 1.96% in the same gene with the germline mutation. Six of fifteen (40%) nasal and two of four (50%) dermal telangiectasia had a detectable somatic second hit. Additional low-level somatic mutations in other genes were identified in several telangiectasias. This is the first report that nasal telangiectasias and solid organ AVMs in HHT are caused by very-low-level somatic biallelic second-hit mutations.

Pulmonary hypertension exacerbated by hereditary hemorrhagic telangiectasia combined with pulmonary arteriovenous fistula and pregnancy status: A case report.

Background: Hereditary hemorrhagic telangiectasia (HHT) is an uncommon autosomal dominant condition. The combination of pregnancy and HHT can exacerbate pulmonary hypertension (PH) and, in severe cases, lead to fatality. Case presentation: The case we presented is a 28-year-old multiparous woman. She developed chest tightness and dyspnea in the second trimester of pregnancy, which was not taken seriously at that time, and the symptoms worsened postpartum. Echocardiography showed elevated pulmonary artery pressure (PAP) and the computerized tomographic pulmonary angiogram revealed a significant pulmonary arteriovenous malformation. The patient's condition continued to deteriorate despite treatment to reduce pulmonary hypertension. We reviewed and updated the history of omission, recurrent epistaxis during pregnancy, and similar symptoms running in her family. Combined with the whole exon genetic testing report revealing the ACVRL1 gene mutation at chr12:52308295, the diagnosis of HHT was established. Four months later, a transcatheter closure of the pulmonary arteriovenous fistula was performed, with satisfying outcomes presenting a decrease of more than 15 mmHg in the pulmonary artery pressure. As of right now, the patient's status is stable during the outpatient follow-up. Conclusions: HHT is a rare condition that typically occurs alongside abnormal communication between pulmonary veins and arteries, leading to a high-flow state in the pulmonary circulation. A pulmonary hypertension crisis can also be triggered by the patient's pregnancy, which further increases blood volume. By reducinhttps://www.ecdc.europa.eu/sites/default/files/documents/Methods-for-the%20detection-and-characterisation-of-SARS-CoV-2-variants-first-update-WHO-20-Dec-2021.pdfg pulmonary vascular flow, catheter closure of the pulmonary arteriovenous fistula decreases pulmonary arterial pressure.

Increased Risk for Infections and Allergic Disease in Hereditary Hemorrhagic Telangiectasia.

Background/Objectives: Hereditary hemorrhagic telangiectasia (HHT) is a rare disorder characterized by dilated blood vessels. Different immunological changes have been described in these patients. In this study, the predisposition of patients with HHT to infections and allergic diseases was assessed. Methods: Patients with HHT completed an online survey in English or German. Their data were compared to non-affected partners or friends. Results: A total of 430 out of 588 respondents with HHT answered our questions about infections and allergies. Patients with HHT suffered significantly more often from various types of allergies than their partners, especially type I allergies (n = 226/276, 82%), and had a higher risk for sinusitis, urinary tract infections, pulmonary infections, and abscesses. A total of 38% of the patients took antibiotics prior to dental or surgical procedures (n = 57/152), and, in 10% of these patients, pulmonary arteriovenous malformations (PAVMs) were not detected. On the other hand, 51% of patients with PAVM did not report a prophylactic antibiotic intake (n = 40/79). The patients who needed iron supplementations suffered more often from sepsis (OR: 9.00, 95%CI: 0.92-88.16). Conclusions: Compared to their non-affected controls, patients with HHT showed an increased risk for infections in different organs and allergic diseases. There is a need for campaigns raising greater awareness recommending prophylactic antibiotic intake in patients with PAVM.

Endothelial-to-Mesenchymal Transition in an Hereditary Hemorrhagic Telangiectasia-like Pediatric Case of Multiple Pulmonary Arteriovenous Malformations.

Pulmonary arteriovenous malformations (PAVMs) are vascular anomalies resulting in abnormal connections between pulmonary arteries and veins. In 80% of cases, PAVMs are present from birth, but clinical manifestations are rarely seen in childhood. These congenital malformations are typically associated with Hereditary Hemorrhagic Telangiectasia (HHT), a rare disease that affects 1 in 5000/8000 individuals. HHT disease is frequently caused by mutations in genes involved in the TGF-ß pathway. However, approximately 15% of patients do not have a genetic diagnosis and, among the genetically diagnosed, more than 33% do not meet the Curaçao criteria. This makes clinical diagnosis even more challenging in the pediatric age group. Here, we introduce an 8-year-old patient bearing a severe phenotype of multiple diffuse PAVMs caused by an unknown mutation which ended in lung transplantation. Phenotypically, the case under study follows a molecular pattern which is HHT-like. Therefore, molecular- biological and cellular-functional analyses have been performed in primary endothelial cells (ECs) isolated from the explanted lung. The findings revealed a loss of functionality in lung endothelial tissue and a stimulation of endothelial-to-mesenchymal transition. Understanding the molecular basis of this transition could potentially offer new therapeutic strategies to delay lung transplantation in severe cases.

ACR Appropriateness Criteria® Pulmonary Arteriovenous Malformation (PAVM): 2023 Update.

Pulmonary arteriovenous malformations (PAVMs) occur in 30% to 50% of patients with hereditary hemorrhagic telangiectasia. Clinical presentations vary from asymptomatic disease to complications resulting from the right to left shunting of blood through the PAVM such as paradoxical stroke, brain abscesses, hypoxemia, and cardiac failure. Radiology plays an important role both in the diagnosis and treatment of PAVM. Based on different clinical scenarios, the appropriate imaging study has been reviewed and is presented in this document. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

Surgical treatment of brain arteriovenous malformations in patients with hereditary hemorrhagic telangiectasia: a single-center experience.

OBJECTIVE: Hereditary hemorrhagic telangiectasia (HHT) is an autosomal-dominant disorder characterized by multiple vascular malformations. Brain arteriovenous malformations (bAVMs) are a significant manifestation of HHT. The surgical management of these lesions in patients with HHT remains debated, with limited literature on postoperative outcomes. The goal of this study was to evaluate the safety and efficacy of surgical treatment for bAVMs in patients with HHT and propose a treatment rationale based on a single-center experience. METHODS: This retrospective review included 20 patients diagnosed with HHT who underwent resection of 23 bAVMs at the Stanford University Medical Center between January 2007 and September 2023. Data were also collected on bAVMs treated conservatively, with embolization, or with radiosurgery at the authors' institution, for comparison. RESULTS: There were 16 Spetzler-Martin (SM) grade I, 6 SM grade II, and 1 SM grade IV bAVM. Six of the bAVMs presented with neurological symptoms (3 with hemorrhage and 3 with focal neurological deficits), while the rest were detected on routine screening. Complete excision was angiographically confirmed in all patients, with a mean overall hospital stay of 2.1 days and a mean follow-up of 36 months. Postoperative complications were limited to transient mild weakness in 2 patients, 1 of whom also had transient speech deficits, and visual field deficits in 3 patients, 2 of whom improved on long-term follow-up. CONCLUSIONS: In this most extensive surgical series published to date, resection of bAVMs in patients with HHT showed favorable outcomes with a low complication rate, suggesting that the benefits of surgery outweigh the risks, especially considering the potential cumulative lifetime risk of hemorrhage. MR arterial spin labeling was found to be the most sensitive noninvasive measure of detecting bAVMs in patients with HHT.

ACR Appropriateness Criteria® Pulmonary arteriovenous malformation (PAVM): 2023 update

Pulmonary arteriovenous malformations (PAVMs) occur in 30% to 50% of patients with hereditary hemorrhagic telangiectasia. Clinical presentations vary from asymptomatic disease to complications resulting from the right to left shunting of blood through the PAVM such as paradoxical stroke, brain abscesses, hypoxemia, and cardiac failure. Radiology plays an important role both in the diagnosis and treatment of PAVM. Based on different clinical scenarios, the appropriate imaging study has been reviewed and is presented in this document. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

Prevalence of hereditary hemorrhagic telangiectasia in a medical care program organization in Buenos Aires, Argentina / Prevalencia de telangiectasia hemorrágica hereditaria en un sistema privado de salud de Buenos Aires, Argentina

Abstract Introduction : Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant vascular dysplasia that might affect 1/5000-10 000 individuals worldwide. It is a rare and underdiagnosed condition. Population-based epidemiological studies are crucial for comprehending and quantifying the impact of this disease. We aim to estimate the prevalence in a Prepaid Health Care System of Buenos Aires, Argentina. Methods : A descriptive cross-sectional study was de signed, which included all patients over 18 years of age affiliated with the Hospital Italiano Medical Care Program (IHMCP), a prepaid health maintenance organization (HMO) of Buenos Aires. For case inclusion, individuals were required to have a clinical diagnosis of HHT. Case detection included the search in our Institutional Registry. The prevalence was calculated by dividing the number of cases of HHT by the total number of all active affiliates at January 2023. Age and gender specific prevalence rates were estimated. Results : 48 cases were reported. The prevalence was 3.2 in 10 000 (IC 95% 2.4-4.2). Specific prevalence in women was 3.9 in 10 000 (IC 95% 2.8-5.5) and in men 2.1 in 10 000 (IC 95% 1.2-3.6). The average age was 54.8 (19), 35 patients were women (72.9%) with an aver age age of 55 (19.9), and 55 (17.2) for men. The most common referrals were physicians (60.4%) followed by family history (18.7%). The 48 patients corresponded to 39 families. Discussion : The prevalence identified in our study is higher than the one documented in other studies.

Resumen Introducción : La telangiectasia hemorrágica heredita ria (HHT) es una displasia vascular que puede afectar a 1 de 5000 a 10 000 personas en el mundo. Es una afección rara y subdiagnosticada. Los estudios epidemiológicos son fundamentales para comprender y cuantificar el im pacto de esta enfermedad. Nuestro objetivo fue estimar la prevalencia en un Sistema Prepago de Atención de la Salud, en Buenos Aires, Argentina. Métodos : Estudio descriptivo transversal en pacientes mayores de 18 años afiliados al Programa de Atención Médica del Hospital Italiano en Buenos Aires (Plan de Sa lud). Para la inclusión de casos, se requería el diagnóstico de HHT. La detección de casos incluyó su búsqueda en nuestro Registro Institucional. La prevalencia se calculó dividiendo el número de casos por el número total de afiliados activos en enero de 2023. Se estimaron tasas específicas por edad y género. Resultados : Se reportaron 48 casos. La prevalencia fue de 3.2 por 10 000 personas (IC 95% 2.4-4.2). La específica en mujeres fue de 3.9 (IC 95% 2.8-5.5) y en hombres de 2.1 por 10 000 (IC 95% 1.2-3.6). La edad promedio fue de 55 años (19), con 35 pacientes mujeres (72.9%) con una edad promedio de 55 años (19.9) y 55 (17.2) para hom bres. La derivación más común fue de médicos (60.4%), seguidas por antecedentes familiares (18.7%). Los 48 pacientes correspondían a 39 familias. Discusión : La prevalencia identificada en nuestro es tudio es más alta que la documentada en otros estudios.

Blood flow regulates acvrl1 transcription via ligand-dependent Alk1 activity.

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant disease characterized by the development of arteriovenous malformations (AVMs) that can result in significant morbidity and mortality. HHT is caused primarily by mutations in bone morphogenetic protein receptors ACVRL1/ALK1, a signaling receptor, or endoglin (ENG), an accessory receptor. Because overexpression of Acvrl1 prevents AVM development in both Acvrl1 and Eng null mice, enhancing ACVRL1 expression may be a promising approach to development of targeted therapies for HHT. Therefore, we sought to understand the molecular mechanism of ACVRL1 regulation. We previously demonstrated in zebrafish embryos that acvrl1 is predominantly expressed in arterial endothelial cells and that expression requires blood flow. Here, we document that flow dependence exhibits regional heterogeneity and that acvrl1 expression is rapidly restored after reinitiation of flow. Furthermore, we find that acvrl1 expression is significantly decreased in mutants that lack the circulating Alk1 ligand, Bmp10, and that, in the absence of flow, intravascular injection of BMP10 or the related ligand, BMP9, restores acvrl1 expression in an Alk1-dependent manner. Using a transgenic acvrl1:egfp reporter line, we find that flow and Bmp10 regulate acvrl1 at the level of transcription. Finally, we observe similar ALK1 ligand-dependent increases in ACVRL1 in human endothelial cells subjected to shear stress. These data suggest that ligand-dependent Alk1 activity acts downstream of blood flow to maintain or enhance acvrl1 expression via a positive feedback mechanism, and that ALK1 activating therapeutics may have dual functionality by increasing both ALK1 signaling flux and ACVRL1 expression.

Employment of diverse in vitro systems for analyzing multiple aspects of disease, hereditary hemorrhagic telangiectasia (HHT).

BACKGROUND: In vitro disease modeling enables translational research by providing insight into disease pathophysiology and molecular mechanisms, leading to the development of novel therapeutics. Nevertheless, in vitro systems have limitations for recapitulating the complexity of tissues, and a single model system is insufficient to gain a comprehensive understanding of a disease. RESULTS: Here we explored the potential of using several models in combination to provide mechanistic insight into hereditary hemorrhagic telangiectasia (HHT), a genetic vascular disorder. Genome editing was performed to establish hPSCs (H9) with ENG haploinsufficiency and several in vitro models were used to recapitulate the functional aspects of the cells that constitute blood vessels. In a 2D culture system, endothelial cells showed early senescence, reduced viability, and heightened susceptibility to apoptotic insults, and smooth muscle cells (SMCs) exhibited similar behavior to their wild-type counterparts. Features of HHT were evident in 3D blood-vessel organoid systems, including thickening of capillary structures, decreased interaction between ECs and surrounding SMCs, and reduced cell viability. Features of ENG haploinsufficiency were observed in arterial and venous EC subtypes, with arterial ECs showing significant impairments. Molecular biological approaches confirmed the significant downregulation of Notch signaling in HHT-ECs. CONCLUSIONS: Overall, we demonstrated refined research strategies to enhance our comprehension of HHT, providing valuable insights for pathogenic analysis and the exploration of innovative therapeutic interventions. Additionally, these results underscore the importance of employing diverse in vitro systems to assess multiple aspects of disease, which is challenging using a single in vitro system.

To Test or Not to Test: A Case Report on Hereditary Hemorrhagic Telangiectasia.

A 50-year-old female patient presenting with joint pains, Raynaud's phenomenon, epistaxis, and telangiectasias was posed with a diagnostic conundrum, i.e., whether to accept the diagnosis of mixed connective tissue disease (MCTD), for which she fulfilled all the criteria, or test for another probable disease, namely hereditary hemorrhagic telangiectasia (HHT), even though only some clinical features were present and all diagnostic criteria were not satisfied. Taking the patient's onset of epistaxis as an important clue, the patient was counseled for genetic testing for HHT, which was positive. Treatment for both MCTD and HHT is underway, and appropriate surveillance is planned for the patient.

De Novo Brain Vascular Malformations in Hereditary Hemorrhagic Telangiectasia.

BACKGROUND: Approximately 10% of people with hereditary hemorrhagic telangiectasia (HHT) have brain vascular malformations (VMs). Few reports describe de novo brain VM formation. International HHT Guidelines recommend initial brain VM screening upon HHT diagnosis in children but do not address rescreening. We aimed to confirm whether brain VMs can form de novo in patients with HHT. METHODS: The Brain Vascular Malformation Consortium HHT project is a 17-center longitudinal study enrolling patients since 2010. We analyzed the database for de novo VMs defined as those detected (1) on follow-up neuroimaging in a patient without previous brain VMs or (2) in a location distinct from previously identified brain VMs and reported those in whom a de novo VM could be confirmed on central neuroimaging review. RESULTS: Of 1909 patients enrolled, 409 (21%) had brain VMs. Seven patients were recorded as having de novo brain VMs, and imaging was available for central review in four. We confirmed that three (0.7% of individuals with brain VMs) had de novo brain VMs (two capillary malformations, one brain arteriovenous malformation) with intervals of six, nine, and 13 years from initial imaging. Two with de novo brain VMs were <18 years. The fourth patient, a child, did not have a de novo brain VM but had a radiologically confirmed increase in size of an existing brain arteriovenous malformation. CONCLUSIONS: Brain VMs can, albeit rarely, form de novo in patients with HHT. Given the potential risk of hemorrhage from brain VMs, regular rescreening in patients with HHT may be warranted.