Hereditary haemorrhagic telangiectasia: current views on genetics and mechanisms of disease

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.

Diffuse pulmonary arteriovenous malformation presenting with secondary polycythemia and headaches: a case report

BACKGROUND

Pulmonary arteriovenous malformations are a relatively uncommon medical condition, affecting roughly 1 in every 2500 individuals. Of those suffering from pulmonary arteriovenous malformations, 80% have an underlying genetic condition: hereditary hemorrhagic telangiectasia.

CASE PRESENTATION

We present the case of a 20-year-old Pakistani male with a history of persistent slower-onset frontal headaches that increased in severity within the course of the day. His hemoglobin was 18 g/dl, indicating polycythemia, for which he had undergone seven venesections in a month previously. His physical examination was unremarkable. His computed tomography scan depicted multiple dilated tortuous vessels with branching linear opacities in the right lower lobe of the lungs. The multiple feeding arteries were supplied by the right main pulmonary artery, and the large draining veins led to the right inferior pulmonary vein. This was identified as a diffuse pulmonary arteriovenous malformation. He was recommended for a right pulmonary artery angiogram. It showed multiple tortuous vessels with a nidus and large draining veins-features of a diffuse arteriovenous malformation in the right lower lobe of the lung consistent with the computed tomography scan. Embolization of two of these vessels feeding the arteriovenous malformation was conducted, using Amplatzer Vascular plug 2, whereas multiple pushable coils (five coils) were used for embolizing the third feeding vessel. This achieved 70-80% successful embolization of right pulmonary AVM; however, some residual flow was still seen in the arteriovenous malformation given the complexity of the lesion. Immediately after, his oxygen saturation improved from 78% to 96%.

CONCLUSION

Diffuse pulmonary arteriovenous malformations, as seen in this patient, are rare, accounting for less than 5% of total pulmonary arteriovenous malformations diagnosed. The patient presented with a complaint of progressive frontal headaches, which can be attributed to low oxygen saturation or the presence of a cerebral arteriovenous malformation. There was no history of hereditary hemorrhagic telangiectasia in the patient's family. Furthermore, although most patients with hereditary hemorrhagic telangiectasia and hence pulmonary arteriovenous malformation have complaints of iron-deficiency anemia, our patient in contrast was suffering from polycythemia. This can be explained as a compensatory mechanism in hypoxemic conditions. Moreover, the patient had no complaint of hemoptysis or epistaxis, giving a varied presentation in comparison with a typical pulmonary arteriovenous malformation.

Inhibition of endothelial histone deacetylase 2 shifts endothelial-mesenchymal transitions in cerebral arteriovenous malformation models

Cerebral arteriovenous malformations (AVMs) are the most common vascular malformations worldwide and the leading cause of hemorrhagic strokes that may result in crippling neurological deficits. Here, using recently generated mouse models, we uncovered that cerebral endothelial cells (ECs) acquired mesenchymal markers and caused vascular malformations. Interestingly, we found that limiting endothelial histone deacetylase 2 (HDAC2) prevented cerebral ECs from undergoing mesenchymal differentiation and reduced cerebral AVMs. We found that endothelial expression of HDAC2 and enhancer of zeste homolog 1 (EZH1) was altered in cerebral AVMs. These alterations changed the abundance of H4K8ac and H3K27me in the genes regulating endothelial and mesenchymal differentiation, which caused the ECs to acquire mesenchymal characteristics and form AVMs. This investigation demonstrated that the induction of HDAC2 altered specific histone modifications, which resulted in mesenchymal characteristics in the ECs and cerebral AVMs. The results provide insight into the epigenetic impact on AVMs.

Understanding hereditary hemorrhagic telangiectasia: From genetic anomalies to systemic manifestations, quality of life, and epistaxis management-Exploring the otolaryngologist's integral role

Hereditary hemorrhagic telangiectasia (HHT), also known as Osler-Rendu-Weber syndrome, is a rare autosomal dominant disorder characterized by vascular malformations. This comprehensive review aimed to provide an overview and summarize various aspects of HHT, including the genetic abnormalities, complications associated with visceral arteriovenous malformations (AVMs), prognosis of HHT, quality of life (QOL), and treatment of epistaxis. In addition, this review highlights the challenges in diagnosing HHT and emphasizes the critical role of otolaryngologists in the early detection of HHT. Otolaryngologists can refer patients with refractory epistaxis for AVM screening to expedite intervention. Mutation of the genes involved in the transforming growth factor-β signaling pathway leads to the incidence of HHT, resulting in the formation of abnormal blood vessel formation. These vascular malformations commonly manifest as telangiectasia on the skin and mucous membranes; however, epistaxis remains the hallmark symptom of HHT. The impact of HHT goes beyond the visible symptoms and often includes the formation of life-threatening visceral AVMs in the lungs, liver, and brain. The prognosis of patients with HHT is closely related to the development of these complications, necessitating timely diagnosis and intervention. Refractory epistaxis diminishes the QOL of patients with HHT. The management of epistaxis ranges from conservative measures to advanced interventions such as prevention, conservative treatments, ablation, surgical procedures, and the administration of anti-angiogenic agents. However, effective management requires a multidisciplinary approach. The diagnosis of HHT remains challenging due to its variable presentation and lack of awareness among physicians. This review highlights the importance of reducing the duration between symptom onset and diagnosis. Otolaryngologists who are experienced in the management of refractory epistaxis can aid in identifying potential cases of HHT. They can facilitate the initiation of screening for visceral AVMs via prompt recognition of the signs and symptoms of HHT, contributing to improved patient outcomes. Early detection and intervention through screening can extend the life expectancy of patients with HHT to levels comparable with that of the general population. In conclusion, this review provides insight into various aspects of HHT and emphasizes the importance of timely diagnosis and intervention in the mitigation of the potentially life-threatening complications associated with this disorder. Otolaryngologists play a critical role in this process, serving as gatekeepers to the identification of cases of HHT and implementation of appropriate screening and management pathways, thereby improving the life expectancy and QOL of patients.

Transcriptional profiling of peripheral blood mononuclear cells identifies inflammatory phenotypes in Ataxia Telangiectasia

INTRODUCTION

Ataxia telangiectasia (A-T) is an autosomal recessive neurodegenerative disease with widespread systemic manifestations and marked variability in clinical phenotypes. In this study, we sought to determine whether transcriptomic profiling of peripheral blood mononuclear cells (PBMCs) defines subsets of individuals with A-T beyond mild and classic phenotypes, enabling identification of novel features for disease classification and treatment response to therapy.

METHODS

Participants with classic A-T (n = 77), mild A-T (n = 13), and unaffected controls (n = 15) were recruited from two outpatient clinics. PBMCs were isolated and bulk RNAseq was performed. Plasma was also isolated in a subset of individuals. Affected individuals were designated mild or classic based on ATM mutations and clinical and laboratory features.

RESULTS

People with classic A-T were more likely to be younger and IgA deficient and to have higher alpha-fetoprotein levels and lower % forced vital capacity compared to individuals with mild A-T. In classic A-T, the expression of genes required for V(D)J recombination was lower, and the expression of genes required for inflammatory activity was higher. We assigned inflammatory scores to study participants and found that inflammatory scores were highly variable among people with classic A-T and that higher scores were associated with lower ATM mRNA levels. Using a cell type deconvolution approach, we inferred that CD4 + T cells and CD8 + T cells were lower in number in people with classic A-T. Finally, we showed that individuals with classic A-T exhibit higher SERPINE1 (PAI-1) mRNA and plasma protein levels, irrespective of age, and higher FLT4 (VEGFR3) and IL6ST (GP130) plasma protein levels compared with mild A-T and controls.

CONCLUSION

Using a transcriptomic approach, we identified novel features and developed an inflammatory score to identify subsets of individuals with different inflammatory phenotypes in A-T. Findings from this study could be used to help direct treatment and to track treatment response to therapy.

Longitudinal Assessment of Curaçao Criteria in Children with Hereditary Hemorrhagic Telangiectasia

OBJECTIVE

To assess the utility of the Curaçao criteria by age over time in children with hereditary hemorrhagic telangiectasia (HHT).

STUDY DESIGN

This was a single-center, retrospective analysis of patients attending the HHT clinic at the Hospital for Sick Children (Toronto, Canada) between 2000 and 2019. The evaluation of the Curaçao criteria was completed during initial and follow-up visits. Screening for pulmonary and brain arteriovenous malformations was completed at 5 yearly intervals.

RESULTS

A total of 116 patients with genetic confirmation of HHT were included in the analysis. At initial screening at a median (IQR) age of 8.4 (2.8, 12.9) years, 41% met criteria for a definite clinical diagnosis (≥3 criteria). In children <6 years at presentation, only 23% fulfilled at least 3 criteria initially. In longitudinal follow-up, 63% reached a definite clinical diagnosis, with a median (IQR) follow-up duration of 5.2 (3.2, 7.9) years (P = .005). Specifically, more patients met the epistaxis and telangiectasia criteria at last visit compared with initial (79% vs 60%; P = .006; 47% vs 30%; P = .02) but not for the arteriovenous malformation criterion (59% vs 57%; P = .65).

CONCLUSIONS

In the pediatric population, most patients do not meet definite clinical criteria of HHT at initial presentation. Although the number of diagnostic criteria met increased over time, mainly due to new onset of epistaxis and telangiectasia, accuracy remained low during follow-up visits. Relying solely on clinical criteria may lead to underdiagnosis of HHT in children.

Hepatic Vascular Variants in Hereditary Haemorrhagic Telangiectasia: Imaging findings

Hereditary haemorrhagic telangiectasia (HHT) is an autosomal dominant disorder characterised by vascular dysplasia. Hepatic vascular malformations (VMs) range from small telangiectases to significant vascular shunting. Here we report two cases of HHT. Case 1 had diffuse ectasia of the hepatic artery along its intrahepatic and extrahepatic course with a hepatic arterial aneurysm. Case 2 presented with ileal and hepatic telangiectases. Knowledge of these vascular variants is indispensable for clinicians and radiologists in aiding diagnosis and surgical and interventional management.

Essential role of the amino-terminal region of Drosha for the Microprocessor function

Drosha is a core component of the Microprocessor complex that cleaves primary-microRNAs (pri-miRNAs) to generate precursor-miRNA and regulates the expression of ∼80 ribosomal protein (RP) genes. Despite the fact that mutations in the amino-terminal region of Drosha (Drosha-NTR) are associated with a vascular disorder, hereditary hemorrhagic telangiectasia, the precise function of Drosha-NTR remains unclear. By deleting exon 5 from the Drosha gene and generating a Drosha mutant lacking the NTR (ΔN), we demonstrate that ΔN is unable to process pri-miRNAs, which leads to a global miRNA depletion, except for the miR-183/96/182 cluster. We find that Argonaute 2 facilitates the processing of the pri-miR-183/96/182 in ΔN cells. Unlike full-length Drosha, ΔN is not degraded under serum starvation, resulting in unregulated RP biogenesis and protein synthesis in ΔN cells, allowing them to evade growth arrest. This study reveals the essential role of Drosha-NTR in miRNA production and nutrient-dependent translational control.

Long-term use of somatostatin analogs for chronic gastrointestinal bleeding in hereditary hemorrhagic telangiectasia

Background

Chronic bleeding due to gastrointestinal (GI) involvement in patients with hemorrhagic hereditary telangiectasia (HHT) can provoke severe anemia with high red blood cells (RBC) transfusion requirements. However, the evidence about how to deal with these patients is scarce. We aimed to assess the long-term efficacy and safety of somatostatin analogs (SA) for anemia management in HHT patients with GI involvement.

Methods

This is a prospective observational study including patients with HHT and GI involvement attended at a referral center. SA were considered for those patients with chronic anemia. Anemia-related variables were compared in patients receiving SA before and during treatment. Patients receiving SA were divided into responders (patients with minimal hemoglobin levels improvement >10 g/L and maintaining hemoglobin levels ≥80 g/L during treatment), and non-responders. Adverse effects during follow-up were collected.

Results

Among 119 HHT patients with GI involvement, 67 (56.3%) received SA. These patients showed lower minimal hemoglobin levels (73 [60-87] vs. 99 [70.2-122.5], p < 0.001), and more RBC transfusion requirements (61.2% vs. 38.5%, p = 0.014) than patients without SA therapy. Median treatment period was 20.9 ± 15.2 months. During treatment, there was a statistically significant improvement in minimum hemoglobin levels (94.7 ± 29.8 g/L vs. 74.7 ± 19.7, p < 0.001) and a reduction of patients with minimal hemoglobin levels <80 g/L (39 vs. 61%, p = 0.007) and RBC transfusions requirement (33.9% vs. 59.3%, p < 0.001). Sixteen (23.9%) patients showed mild adverse effects, mostly diarrhea or abdominal pain, leading to treatment discontinuation in 12 (17.9%) patients. Fifty-nine patients were eligible for efficacy assessment and 32 (54.2%) of them were considered responders. Age was associated with non-responder patients, OR 95% CI; 1.070 (1.014-1.130), p = 0.015.

Conclusion

SA can be considered a long-term effective and safe option for anemia management in HHT patients with GI bleeding. Older age is associated with poorer response.

Recent Development of Advanced Fluorescent Molecular Probes for Organelle-Targeted Cell Imaging

Fluorescent molecular probes are very powerful tools that have been generally applied in cell imaging in the research fields of biology, pathology, pharmacology, biochemistry, and medical science. In the last couple of decades, numerous molecular probes endowed with high specificity to particular organelles have been designed to illustrate intracellular images in more detail at the subcellular level. Nowadays, the development of cell biology has enabled the investigation process to go deeply into cells, even at the molecular level. Therefore, probes that can sketch a particular organelle's location while responding to certain parameters to evaluate intracellular bioprocesses are under urgent demand. It is significant to understand the basic ideas of organelle properties, as well as the vital substances related to each unique organelle, for the design of probes with high specificity and efficiency. In this review, we summarize representative multifunctional fluorescent molecular probes developed in the last decade. We focus on probes that can specially target nuclei, mitochondria, endoplasmic reticulums, and lysosomes. In each section, we first briefly introduce the significance and properties of different organelles. We then discuss how probes are designed to make them highly organelle-specific. Finally, we also consider how probes are constructed to endow them with additional functions to recognize particular physical/chemical signals of targeted organelles. Moreover, a perspective on the challenges in future applications of highly specific molecular probes in cell imaging is also proposed. We hope that this review can provide researchers with additional conceptual information about developing probes for cell imaging, assisting scientists interested in molecular biology, cell biology, and biochemistry to accelerate their scientific studies.

Genetics of brain arteriovenous malformations and cerebral cavernous malformations

Cerebrovascular malformations comprise abnormal development of cerebral vasculature. They can result in hemorrhagic stroke due to rupture of lesions as well as seizures and neurological defects. The most common forms of cerebrovascular malformations are brain arteriovenous malformations (bAVMs) and cerebral cavernous malformations (CCMs). They occur in both sporadic and inherited forms. Rapidly evolving molecular genetic methodologies have helped to identify causative or associated genes involved in genesis of bAVMs and CCMs. In this review, we highlight the current knowledge regarding the genetic basis of these malformations.

Tranexamic acid may be a useful pharmacotherapy for endoscopically resistant small bowel angiodysplasia

Small bowel angiodysplasia (SBAD) is reported to account for nearly 50% of cases of small bowel bleeding. When SBAD occurs frequently, it is difficult to treat all the angiodysplasias endoscopically, and gastrointestinal bleeding often recurs. Hormone therapy, somatostatin analogs, thalidomide and vascular endothelial growth factor (VEGF)-neutralizing antibodies have been reported to reduce gastrointestinal angiodysplasia (GIAD) bleeding. However, there is no strong evidence to recommend them. Also, there are no guidelines for their use. Hereditary hemorrhagic telangiectasia (HHT) is a hereditary disease caused by abnormalities in VEGF, resulting in multiple GIADs. A treatment guideline has been created for GIAD in HHT, and the use of tranexamic acid, an antifibrinolytic agent, is the first recommendation pharmacotherapy for GIAD with gastrointestinal bleeding that is difficult to treat endoscopically. It has been reported that fibrinolysis is accelerated in GIAD patients who are not HHT, similar to HHT patients. The use of tranexamic acid for gastric antral vascular ectasia in GIAD has been reported to be useful. However, there are very few reports of its use for SBAD. There are concerns with tranexamic acid use regarding the development of thrombosis/embolism, but there are few reports of such side effects. Future clinical trials including tranexamic acid for SBAD are desired.

Hereditary Hemorrhagic Telangiectasia in Pediatric Age: Focus on Genetics and Diagnosis

Hereditary Hemorrhagic Telangiectasia (HHT) or Rendu-Osler-Weber Syndrome (ROW) is an autosomal dominant vascular disease, with an estimated prevalence of 1:5000. Genes associated with HHT are ACVRL1, ENG, SMAD4, and GDF2, all encoding for proteins involved in the TGFβ/BMPs signaling pathway. The clinical diagnosis of HHT is made according to the "Curaçao Criteria," based on the main features of the disease: recurrent and spontaneous epistaxis, muco-cutaneous telangiectases, arteriovenous malformations in the lungs, liver, and brain, and familiarity. Since the clinical signs of HHT can be misinterpreted, and the primary symptom of HHT, epistaxis, is common in the general population, the disease is underdiagnosed. Although HHT exhibits a complete penetrance after the age of 40, young subjects may also present symptoms of the disease and are at risk of severe complications. Here we review the literature reporting data from clinical, diagnostic, and molecular studies on the HHT pediatric population.

Update on pulmonary arteriovenous malformations

This review aimed to provide an overview of pulmonary arteriovenous malformations, including the major clinical and radiological presentations, investigation, and treatment algorithm of the condition. The primary etiology of pulmonary arteriovenous malformations is hereditary hemorrhagic telangiectasia (HHT), also known as Rendu-Osler-Weber syndrome, with mutations in the ENG gene on chromosome 9 (HHT type 1) or in the ACVRL1/ALK1 complex (HHT type 2). Epistaxis should always be evaluated when repeated, when associated with anemia, and in some cases of hypoxemia. In the investigation, contrast echocardiography and chest CT are essential for evaluating this condition. Embolization is the best treatment choice, especially for correction in cases of hypoxemia or to avoid systemic infections. Finally, disease management was addressed in special conditions such as pregnancy. CT follow-up should be performed every 3-5 years, depending on the size of the afferent and efferent vessels, and antibiotic prophylactic care should always be oriented. Ultimately, knowledge of the disease by health professionals is a crucial point for the early diagnosis of these patients in clinical practice, which can potentially modify the natural course of the disease.

Role of octreotide in small bowel bleeding

Gastrointestinal bleeding accounts for a drastic negative impact on the quality of the patients’ lives as it requires multiple diagnostic and therapeutic interventions to identify the source of the bleeding. Small bowel bleeding is the least common cause of gastrointestinal bleeding. However, it is responsible for the majority of complaints from patients with persisting or recurring bleeding where the primary source of bleeding cannot be identified despite investigation. A somatostatin analog known as octreotide is among the medical treatment modalities currently used to manage small bowel bleeding. This medication helps control symptoms of gastrointestinal bleeding by augmenting platelet aggregation, decreasing splanchnic blood flow, and antagonizing angiogenesis. In this review article, we will highlight the clinical efficacy of octreotide in small bowel bleeding and its subsequent effect on morbidity and mortality.

Prevalence of Intracranial Aneurysms in Hereditary Hemorrhagic Telangiectasia: Report from a Single Reference Center

BACKGROUND AND PURPOSE

Neurologic manifestations in hereditary hemorrhagic telangiectasia include an increased incidence of brain abscesses and ischemic strokes due to paradoxic embolization in addition to a wide spectrum of symptoms and complications due to typical brain vascular malformations. Intracranial aneurysms are not part of this brain vascular malformation spectrum. The aim of this study was to determine their prevalence in patients with hereditary hemorrhagic telangiectasia.

MATERIALS AND METHODS

This was a single-center, retrospective study. Adult patients from the institutional Hereditary Hemorrhagic Telangiectasia registry with a definitive diagnosis of hereditary hemorrhagic telangiectasia and an available report or angiographic imaging study were included and reviewed to determine the intracranial aneurysm prevalence. In addition, the morphologic characteristics of intracranial aneurysms and possible associated risk factors were collected.

RESULTS

Two hundred twenty-eight patients were analyzed. Thirty-seven aneurysms in 33 patients (14.5%; 95% CI, 9.9%-19%) were found. The median diameter of intracranial aneurysms was 3.2 mm (interquartile range, 2.6-4.4 mm). No association between intracranial aneurysm and sex, age, or genetic background was noted. There were no subarachnoid hemorrhagic events due to intracranial aneurysm rupture.

CONCLUSIONS

Due to the high prevalence of intracranial aneurysms in adult patients with hereditary hemorrhagic telangiectasia, further studies regarding bleeding risks and monitoring should be addressed.

Neurovascular Manifestations in Pediatric Patients With Hereditary Haemorrhagic Telangiectasia

BACKGROUND

Hereditary hemorrhagic telangiectasia (HHT) is a multiorgan vascular dysplasia with limited data regarding its neurovascular manifestations and genotype-phenotype correlation in children. The objective of this study was to describe the neurovascular findings in a large cohort of children with HHT and correlate between phenotype and genotype.

METHODS

This retrospective study was conducted on 221 children (<18 years) with a definite or possible diagnosis of HHT based on Curacao criteria, or with positive genetics for the mutated genes of ENG, ACVRL-1, and SMAD-4, who also underwent brain MRI and/or conventional angiography. Demographic and clinical information, imaging findings, and follow up information were gathered.

RESULTS

Two hundred twenty-one children with HHT (70.6% genetically confirmed, and 99.5% positive family history) were included, with a median age of 7 years (interquartile range: 3 to 11 years) and 58.8% male predominance. Neurovascular lesions were found in 64 of 221 (28.9%), with 3.1% prevalence of intracranial hemorrhage. The most commonly observed vascular malformations were developmental venous anomalies (48.5%) and brain arteriovenous malformations (AVMs) (31.2%), followed by capillary malformations (14.1%). Multiple AVMs were seen in 10.0% of the cohort. We found no instances of de novo AVM (1281.8 patient-years).A significantly higher proportion of patients with ENG mutations (19.7%) had brain AVM than those with ACVRL-1 (4.9%) and SMAD-4 (0%) mutations (P < 0.01). There was no significant difference in the hemorrhagic risk of shunting lesions associated with ENG (35.3%) or ACVRL-1 (33.3%) positivity (P = 0.9).

CONCLUSIONS

We describe the neurovascular imaging and genetic findings from a large pediatric cohort of HHT, to enhance clinical awareness and guide management of patients with HHT.

Sclerotherapy for Hereditary Hemorrhagic Telangiectasia-Related Epistaxis: A Systematic Review

OBJECTIVES

Hereditary hemorrhagic telangiectasia (HHT) is a common inherited condition characterized by mucosal telangiectasias, recurrent epistaxis, and arteriovenous malformations. HHT results in detriment to quality of life. Morbidity and mortality result from severe anemia. Conventional interventions for HHT-related epistaxis include nasal packing, diathermy, lasers, coblation, microdebridement, bevacizumab (topical and systemic), as well as septodermoplasty and nasal closure. Sclerotherapy has been recently described in the literature as a novel approach to HHT-related epistaxis. We hypothesize that sclerotherapy is an effective treatment for HHT-related epistaxis and improves upon the current standard of care for this disease.

METHODS

A systematic review was conducted to study sclerotherapy for treating HHT-related epistaxis. Ovid MEDLINE, Ovid EMBASE, Scopus, and Web of Science were searched. Articles were evaluated and excluded according to PRISMA guidelines and reviewed by 2 authors. Reported variables included number of injections, months of follow up, changes in Epistaxis Severity Score, previous treatments used to control epistaxis, and post-injection side effects.

RESULTS

Seven studies with a total of 196 patients met inclusion criteria. Three studies reported significant improvement as measured by the Epistaxis Severity Score scale. One reported improvement through subjective patient surveys and others used the Bergler-Sadick scale to measure frequency and intensity of epistaxis. All studies reported improvement in HHT-related epistaxis. The lack of uniform reporting measures however precluded formal meta-analysis.

CONCLUSIONS

Based on limited data, sclerotherapy appears to be effective for treating HHT-related epistaxis and offers promise for treating this recalcitrant condition. However, larger, prospective, multi-centered studies using universally validated instruments for epistaxis are needed to definitively evaluate outcomes from sclerotherapy.

Snake Technique in Osler's Disease-associated Thoracoabdominal Aortic Aneurysm

Osler's disease is an autosomal dominant disorder characterized by epistaxis, telangiectases, and arteriovenous malformations of the internal organs. We, herein, report the first published case of dissecting thoracoabdominal aortic aneurysm repair in a 66 year-old woman with hereditary hemorrhagic telangiectasia associated with activin receptor-like kinase 1 gene mutations. We maintained the activated clotting time around 400 seconds during cardiopulmonary bypass to avoid lethal hemorrhage from telangiectases or arteriovenous malformations. The Adamkiewicz artery could not be identified on imaging studies preoperatively. We, therefore, used the 'Snake technique' for intercostal revascularization, which was effective in preventing paraplegia.

Clinical characteristics and prognosis analysis of idiopathic and hereditary pulmonary hypertension patients with ACVRL1 gene mutations

Pulmonary arterial hypertension is a kind of heart and lung vascular disease with low incidence and poor prognosis. Genetic variants are the important factors of pulmonary arterial hypertension. The mutations of activin receptor-like kinase-1 (ACVRL1) could cause pulmonary arteriole obstruction and occlusion in pulmonary arterial hypertension patients. The ACVRL1 gene mutation and clinical characteristics of Chinese idiopathic or hereditary pulmonary hypertension (IPAH/HPAH) patients are still unclear. This study aimed to retrospectively study the mutation characteristics of ACVRL1 gene in Chinese IPAH/HPAH patients and its effect on clinical prognosis. We analyzed the clinical, functional, hemodynamic and mutation characteristics of 12 IPAH/HPAH patients with ACVRL1 mutations and compared with 94 IPAH/HPAH patients (27 patients carried bone morphogenetic protein receptor type 2 (BMPR2) mutations and 67 without mutations). All ACVRL1 mutations of 12 patients were single nucleotide missense mutations. The ratio of male to female in 12 patients was 1:1. The diagnosis age of ACVRL1 mutation patients was younger than that of BMPR2 mutation patients (13.6 ± 11.3 years vs. 16.0 ± 12.9 years) but higher than that of patients without mutations (13.6 ± 11.3 years vs. 8.8 ± 8.5 years, p = 0.006). IPAH/HPAH patients with ACVRL1 mutation have rapid disease progresses, high overall mortality rate (approximately 50%) and no response to the acute pulmonary vasodilation test. In conclusion, this is the first study to analyze the ACVRL1 gene mutation and clinical characteristics of Chinese IPAH/HPAH patients. It is beneficial to screen ACVRL1 gene mutation for IPAH/HPAH patients to facilitate genetic counseling and early prevention and treatment.

Mutational and clinical spectrum of Japanese patients with hereditary hemorrhagic telangiectasia

Background

Hereditary hemorrhagic telangiectasia (HHT) is a dominantly inherited vascular disorder characterized by recurrent epistaxis, skin/mucocutaneous telangiectasia, and organ/visceral arteriovenous malformations (AVM). HHT is mostly caused by mutations either in the ENG or ACVRL1 genes, and there are regional differences in the breakdown of causative genes. The clinical presentation is also variable between populations suggesting the influence of environmental or genetic backgrounds. In this study, we report the largest series of mutational and clinical analyses for East Asians.

Methods

Using DNAs derived from peripheral blood leukocytes of 281 Japanese HHT patients from 150 families, all exons and exon–intron boundaries of the ENG, ACVRL1, and SMAD4 genes were sequenced either by Sanger sequencing or by the next-generation sequencing. Deletions/amplifications were analyzed by the multiplex ligation-dependent probe amplification analyses. Clinical information was obtained by chart review.

Results

In total, 80 and 59 pathogenic/likely pathogenic variants were identified in the ENG and ACVRL1 genes, respectively. No pathogenic variants were identified in the SMAD4 gene. In the ENG gene, the majority (60/80) of the pathogenic variants were private mutations unique to a single family, and the variants were widely distributed without any distinct hot spots. In the ACVRL1 gene, the variants were more commonly found in exons 5–10 which encompasses the serine/threonine kinase domain. Of these, 25/59 variants were unique to a single family while those in exons 8–10 tended to be shared by multiple (2–7) families. Pulmonary and cerebral AVMs were more commonly found in ENG-HHT (69.1 vs. 14.4%, 34.0 vs. 5.2%) while hepatic AVM was more common in ACVRL1-HHT (31.5 vs. 73.2%). Notable differences include an increased incidence of cerebral (34.0% in ENG-HHT and 5.2% in ACVRL1-HHT), spinal (2.5% in ENG-HHT and 1.0% in ACVL1-HHT), and gastric AVM (13.0% in ENG-HHT, 26.8% in ACVRL1-HHT) in our cohort. Intrafamilial phenotypic heterogeneity not related to the age of examination was observed in 71.4% and 24.1% of ENG- and ACVRL1-HHT, respectively.

Conclusions

In a large Japanese cohort, ENG-HHT was 1.35 times more common than ACVRL1-HHT. The phenotypic presentations were similar to the previous reports although the cerebral, spinal, and gastric AVMs were more common.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12920-021-01139-y.

Connective Tissue Disorders and Cardiovascular Complications: The Indomitable Role of Transforming Growth Factor-β Signaling

Marfan Syndrome (MFS) and Loeys-Dietz Syndrome (LDS) represent heritable connective tissue disorders that segregate with a similar pattern of cardiovascular defects (thoracic aortic aneurysm, mitral valve prolapse/regurgitation, and aortic dilatation with regurgitation). This pattern of cardiovascular defects appears to be expressed along a spectrum of severity in many heritable connective tissue disorders and raises suspicion of a relationship between the normal development of connective tissues and the cardiovascular system. With overwhelming evidence of the involvement of aberrant Transforming Growth Factor-beta (TGF-β) signaling in MFS and LDS, this signaling pathway may represent the common link in the relationship between connective tissue disorders and their associated cardiovascular complications. To further explore this hypothetical link, this chapter will review the TGF-β signaling pathway, the heritable connective tissue syndromes related to aberrant TGF-β signaling, and will discuss the pathogenic contribution of TGF-β to these syndromes with a primary focus on the cardiovascular system.

A novel endoglin mutation in a family with hereditary hemorrhagic telangiectasia: a case report

Hereditary hemorrhagic telangiectasis (HHT) is an autosomal dominant vascular disease, and approximately 80% of all HHT cases are caused by gene mutation. In this report, we analyzed the case of an 11-year-old girl who had intracranial bleeding when she was 7 years old. Her brain computed tomography (CT) scans and craniocerebral angiography results revealed that she had multiple cerebral arteriovenous malformations (CAVMs). Cardiac computed tomography angiography (CTA) revealed a pulmonary arteriovenous malformation (PAVM) located in a segment of the left lung. This patient's primary diagnosis was of CAVMs and PAVMs. Both cerebral vascular embolization therapy and interventional treatment for PAVMs were performed to treat these respective conditions. The operations were successful and the patient's prognosis was good. To confirm the patient's diagnosis and the cause of her conditions, peripheral blood was collected from her and her family for whole-exome sequencing (WES). Sanger sequencing was used to verify these results and STRUM software was used to predict the presence of mutant proteins. We found a new mutation of the endoglin (ENG) gene present in this family; this mutation is known as c.1466del (p.Gln489Argfs*2). The patient's mother was a carrier of this heterozygous mutation. STRUM software confirmed that the configuration of the ENG protein p.Gln489Argfs2 site changed with this mutation. We believe this c.1466del (p.Gln489Argfs*2) mutation affects ENG protein function, and the resultant ENG protein dysfunction leads to HHT. When a child has multiple vascular malformation, HHT should be considered as a primary diagnosis.

First Time Wheezing in a 2-Year-Old

Pediatric patients with respiratory signs and symptoms who are found to be wheezing present a diagnostic dilemma to pediatricians. The majority of these cases are diagnosed as some degree of reactive airway disease, either as viral bronchiolitis or asthma. In this scenario, a patient with wheezing was initially given 2 courses of appropriate antibiotics on the basis of the duration and concurrence of other symptoms. However, he was subsequently referred to a pediatric pulmonologist for further workup after failure to improve and persistent oxygen saturations in the low-to-mid 90s. More extensive testing was completed by the pediatric pulmonologist, in addition to a short hospital admission. A rigid bronchoscopy was eventually completed, which revealed small pieces of partially digested material. Although his persistent cough resolved, his saturations continued to be suboptimal. A chest computed tomography scan with contrast was then completed, which eventually led to his diagnosis and appropriate treatment and resolution of his symptoms.

Sclerotherapy Versus Cautery/Laser Treatment for Epistaxis in Hereditary Hemorrhagic Telangiectasia

OBJECTIVES/HYPOTHESIS

Surgical interventions for epistaxis management in hereditary hemorrhagic telangiectasia (HHT) demonstrate short-term success and require repeated procedures for disease control. Although electrocautery and/or laser photocoagulation (C ± L) are most frequently performed, sodium tetradecyl sclerotherapy (STS) is emerging as a promising newer treatment. We hypothesized that in a 24-month time period, STS would require fewer treatments than C ± L to maintain epistaxis severity within the mild range.

STUDY DESIGN

Retrospective study.

METHODS

We retrospectively assessed 67 patients with HHT with moderate and severe epistaxis that were treated periodically with C ± L (34 patients) versus STS (33 patients). The primary outcome was the number of procedures needed to maintain the epistaxis severity score (ESS) as mild. Secondary outcomes assessed for differences in postoperative complications, hemoglobin levels, iron stores, hematologic support, and quality-of-life (QoL) scores.

RESULTS

To maintain ESS in the mild range, 1.6 STS procedures (range, 1-4) were performed versus 3.6 C ± L procedures (range, 1-8) (P = .003). Significant postoperative differences included reduction in nasal crusting (3% vs. 32%, P = .001), foul odor (3% vs. 35%, P < .001), and septal perforation (3% vs. 29%, P = .006) after STS. There were no significant differences between the two treatments in hemoglobin levels, iron stores, hematologic support, or QoL scores.

CONCLUSION

STS is able to attain satisfactory epistaxis control with significantly fewer procedures and lower postoperative complications than C ± L. STS should be considered as the initial surgical intervention for epistaxis in patients with HHT.

LEVEL OF EVIDENCE

IV Laryngoscope, 2021.

Myocardial Infarction in a Patient With Hereditary Hemorrhagic Telangiectasia: A Case Report and Review of Literature

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant disorder that results in vascular defects and arteriovenous malformations. We present a 25-year-old male with a past medical history of HHT who came in with chest pain and was found to have an ST-elevation myocardial infarction (STEMI) and subsequently received a bare-metal stent to the mid-left anterior descending artery (LAD). Although there is a predisposition for bleeding, HHT can lead to thrombotic manifestations such as myocardial infarction (MI), as seen in our patient. Healthcare providers should be aware of this association to be able to efficiently diagnose acute coronary syndrome in HHT patients. Further studies are required to assess the efficacy of bare-metal stents in HHT patients who present with an MI.

Pulmonary Vascular Complications in Hereditary Hemorrhagic Telangiectasia and the Underlying Pathophysiology

In this review, we discuss the role of transforming growth factor-beta (TGF-β) in the development of pulmonary vascular disease (PVD), both pulmonary arteriovenous malformations (AVM) and pulmonary hypertension (PH), in hereditary hemorrhagic telangiectasia (HHT). HHT or Rendu-Osler-Weber disease is an autosomal dominant genetic disorder with an estimated prevalence of 1 in 5000 persons and characterized by epistaxis, telangiectasia and AVMs in more than 80% of cases, HHT is caused by a mutation in the ENG gene on chromosome 9 encoding for the protein endoglin or activin receptor-like kinase 1 (ACVRL1) gene on chromosome 12 encoding for the protein ALK-1, resulting in HHT type 1 or HHT type 2, respectively. A third disease-causing mutation has been found in the SMAD-4 gene, causing a combination of HHT and juvenile polyposis coli. All three genes play a role in the TGF-β signaling pathway that is essential in angiogenesis where it plays a pivotal role in neoangiogenesis, vessel maturation and stabilization. PH is characterized by elevated mean pulmonary arterial pressure caused by a variety of different underlying pathologies. HHT carries an additional increased risk of PH because of high cardiac output as a result of anemia and shunting through hepatic AVMs, or development of pulmonary arterial hypertension due to interference of the TGF-β pathway. HHT in combination with PH is associated with a worse prognosis due to right-sided cardiac failure. The treatment of PVD in HHT includes medical or interventional therapy.

Mutational and phenotypic characterization of hereditary hemorrhagic telangiectasia

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant vascular dysplasia. Care delivery for HHT patients is impeded by the need for laborious, repeated phenotyping and gaps in knowledge regarding the relationships between causal DNA variants in ENG, ACVRL1, SMAD4 and GDF2, and clinical manifestations. To address this, we analyzed DNA samples from 183 previously uncharacterized, unrelated HHT and suspected HHT cases using the ThromboGenomics high-throughput sequencing platform. We identified 127 rare variants across 168 heterozygous genotypes. Applying modified American College of Medical Genetics and Genomics Guidelines, 106 variants were classified as pathogenic/likely pathogenic and 21 as nonpathogenic (variant of uncertain significance/benign). Unlike the protein products of ACVRL1 and SMAD4, the extracellular ENG amino acids are not strongly conserved. Our inferences of the functional consequences of causal variants in ENG were therefore informed by the crystal structure of endoglin. We then compared the accuracy of predictions of the causal gene blinded to the genetic data using 2 approaches: subjective clinical predictions and statistical predictions based on 8 Human Phenotype Ontology terms. Both approaches had some predictive power, but they were insufficiently accurate to be used clinically, without genetic testing. The distributions of red cell indices differed by causal gene but not sufficiently for clinical use in isolation from genetic data. We conclude that parallel sequencing of the 4 known HHT genes, multidisciplinary team review of variant calls in the context of detailed clinical information, and statistical and structural modeling improve the prognostication and treatment of HHT.

Genetic variants and clinical phenotypes in Korean patients with hereditary hemorrhagic telangiectasia

Objectives

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant vascular disorder characterized by recurrent epistaxis, telangiectasia, and visceral arteriovenous malformations (AVMs). Activin A receptor-like type 1 (ACVRL1/ALK1) and endoglin (ENG) are the principal genes whose mutations cause HHT. No multicenter study has yet investigated correlations between genetic variations and clinical outcomes in Korean HHT patients.

Methods

Seventy-two members from 40 families suspected to have HHT based on symptoms were genetically screened for pathogenic variants of ACVRL1 and ENG. Patients with genetically diagnosed HHT were also evaluated.

Results

In the HHT genetic screening, 42 patients from 24 of the 40 families had genetic variants that met the pathogenic criteria (pathogenic very strong, pathogenic strong, pathogenic moderate, or pathogenic supporting) based on the American College of Medical Genetics and Genomics Standards and Guidelines for either ENG or ACVRL1: 26 from 12 families (50%) for ENG, and 16 from 12 families (50%) for ACVRL1. Diagnostic screening of 42 genetically positive HHT patients based on the Curaçao criteria revealed that 24 patients (57%) were classified as having definite HHT, 17 (41%) as having probable HHT, and 1 (2%) as unlikely to have HHT. Epistaxis was the most common clinical presentation (38/42, 90%), followed by visceral AVMs (24/42, 57%) and telangiectasia (21/42, 50%). Five patients (12%) did not have a family history of HHT clinical symptoms.

Conclusion

Only approximately half of patients with ACVRL1 or ENG genetic variants could be clinically diagnosed as having definite HHT, suggesting that genetic screening is important to confirm the diagnosis.

BMP Receptor Inhibition Enhances Tissue Repair in Endoglin Heterozygous Mice

Hereditary hemorrhagic telangiectasia type 1 (HHT1) is a severe vascular disorder caused by mutations in the TGFβ/BMP co-receptor endoglin. Endoglin haploinsufficiency results in vascular malformations and impaired neoangiogenesis. Furthermore, HHT1 patients display an impaired immune response. To date it is not fully understood how endoglin haploinsufficient immune cells contribute to HHT1 pathology. Therefore, we investigated the immune response during tissue repair in Eng+/- mice, a model for HHT1. Eng+/- mice exhibited prolonged infiltration of macrophages after experimentally induced myocardial infarction. Moreover, there was an increased number of inflammatory M1-like macrophages (Ly6Chigh/CD206-) at the expense of reparative M2-like macrophages (Ly6Clow/CD206+). Interestingly, HHT1 patients also showed an increased number of inflammatory macrophages. In vitro analysis revealed that TGFβ-induced differentiation of Eng+/- monocytes into M2-like macrophages was blunted. Inhibiting BMP signaling by treating monocytes with LDN-193189 normalized their differentiation. Finally, LDN treatment improved heart function after MI and enhanced vascularization in both wild type and Eng+/- mice. The beneficial effect of LDN was also observed in the hind limb ischemia model. While blood flow recovery was hampered in vehicle-treated animals, LDN treatment improved tissue perfusion recovery in Eng+/- mice. In conclusion, BMPR kinase inhibition restored HHT1 macrophage imbalance in vitro and improved tissue repair after ischemic injury in Eng+/- mice.

Investigation of the role of platelets in the aetiopathogenesis of adenomyosis

RESEARCH QUESTION

Do platelets aggregate in adenomyotic lesions and participate in adenomyosis pathogenesis and related fibrosis?

DESIGN

Eutopic and ectopic endometrium from 17 patients with adenomyosis and endometrium from 23 healthy controls were collected. Immunohistochemical analyses of platelet marker CD41, transforming growth factor beta 1 (TGF-β1) and vascular endothelial growth factor (VEGF) were performed to investigate aggregation and activation of platelets in the stroma. Picrosirius staining was carried out to evaluate the extent of fibrotic tissue.

RESULTS

Stroma in the control group showed higher CD41 staining levels than ectopic stroma from patients with adenomyosis (P < 0.001). In patients with adenomyosis, eutopic stroma expressed more extensive CD41 staining than ectopic stroma (P < 0.0001). Stroma in the control group exhibited higher TGF-β1 expression than eutopic and ectopic stroma from adenomyosis patients (P = 0.009 and P < 0.0001). Stroma in the control group also expressed higher VEGF levels than ectopic stroma from patients with adenomyosis (P < 0.001). In patients with adenomyosis, eutopic stroma showed higher VEGF expression than ectopic stroma (P = 0.021). Stroma in ectopic endometrium from adenomyosis patients displayed greater Picrosirius staining compared with both eutopic stroma from adenomyosis patients and stroma in the control group (P < 0.0001).

CONCLUSION

The results of this study did not detect a primary role for platelet activation or aggregation in the pathophysiological process of adenomyosis. Higher rates of collagen fibres were found in adenomyotic lesions, likely to be related to a TGF-β1-independent pathway. Collagen fibre deposition was more extensive in adenomyotic lesions, consistent with fibrosis.

Hereditary hemorrhagic telangiectasia presenting as a recurrent epistaxis in an adolescent: A case report

BACKGROUND

Epistaxis can be an isolated finding or a manifestation of a systemic disease. Some of the potential etiologies are usage of anticoagulants, bleeding disorders, vascular aneurysms, nasal neoplasm, hypertension and nasal steroids. Hereditary hemorrhagic telangiectasia (HHT) as a cause of recurrent epistaxis is uncommon.

CASE SUMMARY

In this report, we describe an 18-year-old adolescent with recurrent epistaxis, mucocutaneous telangiectasia and family history of HHT, consistent with HHT.

CONCLUSION

Timely diagnosis is needed not only to treat the epistaxis but also to be vigilant for other serious manifestations of this condition.

Genetic syndromes with vascular malformations - update on molecular background and diagnostics

Vascular malformations are present in a great variety of congenital syndromes, either as the predominant or additional feature. They pose a major challenge to the clinician: due to significant phenotype overlap, a precise diagnosis is often difficult to obtain, some of the malformations carry a risk of life threatening complications and, for many entities, treatment is not well established. To facilitate their recognition and aid in differentiation, we present a selection of notable congenital disorders of vascular system development, distinguishing between the heritable germinal and sporadic somatic mutations as their causes. Clinical features, genetic background and comprehensible description of molecular mechanisms is provided for each entity.

Brain vascular biology

The complex development of the brain vascular system can be broken down by embryonic stages and anatomic locations, which are tightly regulated by different factors and pathways in time and spatially. The adult brain is relatively quiescent in angiogenesis. However, under disease conditions, such as trauma, stroke, or tumor, angiogenesis can be activated in the adult brain. Disruption of any of the factors or pathways may lead to malformed vessel development. In this chapter, we will discuss factors and pathways involved in normal brain vasculogenesis and vascular maturation, and the pathogenesis of several brain vascular malformations.

Potential Second-Hits in Hereditary Hemorrhagic Telangiectasia

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant genetic disorder that presents with telangiectases in skin and mucosae, and arteriovenous malformations (AVMs) in internal organs such as lungs, liver, and brain. Mutations in ENG (endoglin), ACVRL1 (ALK1), and MADH4 (Smad4) genes account for over 95% of HHT. Localized telangiectases and AVMs are present in different organs, with frequencies which differ among affected individuals. By itself, HHT gene heterozygosity does not account for the focal nature and varying presentation of the vascular lesions leading to the hypothesis of a “second-hit” that triggers the lesions. Accumulating research has identified a variety of triggers that may synergize with HHT gene heterozygosity to generate the vascular lesions. Among the postulated second-hits are: mechanical trauma, light, inflammation, vascular injury, angiogenic stimuli, shear stress, modifier genes, and somatic mutations in the wildtype HHT gene allele. The aim of this review is to summarize these triggers, as well as the functional mechanisms involved.

Clinical Analysis of Transcatheter Embolotherapy for Congenital Pulmonary Arteriovenous Fistulas in Children

Objective: To summarize the clinical features and therapeutic effects of transcatheter embolotherapy for congenital pulmonary arteriovenous fistulas (PAVFs) in children, and to explore the method and therapeutic principle of transcatheter embolotherapy for congenital PAVFs in children.Method: We retrospectively reviewed nine patients with PAVF who underwent transcatheter embolotherapy in the Children’s Hospital of Chongqing Medical University from July 2004 to July 2019, including the demographic characteristics, clinical manifestations, efficiency of closure, and follow-up.Results: Transcatheter embolotherapy was successful in all cases, and the symptom remission rate was 100% during the follow-up. No residual shunts or other complications occurred during the follow-up period. Compared with before embolotherapy, there were significant changes in the percentage of saturated oxyhemoglobin and total hemoglobin level at the last follow-up (t=10.06, P=0.000; t=3.055, P=0.0076). No significant difference was observed in pulmonary artery pressure before and after embolotherapy (t=0.13, P=0.90).Conclusions: Transcatheter embolotherapy offers the advantages of safety, with a decreased risk of trauma and a specific effect of treatment, and therefore is recommended as the first-line treatment for congenital PAVFs in children. However, continued research is necessary to understand the full potential of transcatheter embolotherapy.

Endoplasmic Reticulum Associated Protein Degradation (ERAD) in the Pathology of Diseases Related to TGFβ Signaling Pathway: Future Therapeutic Perspectives

The transforming growth factor signaling pathway (TGFβ) controls a wide range of cellular activities in adulthood as well as during embryogenesis including cell growth, differentiation, apoptosis, immunological responses and other cellular functions. Therefore, germline mutations in components of the pathway have given rise to a heterogeneous spectrum of hereditary diseases with variable phenotypes associated with malformations in the cardiovascular, muscular and skeletal systems. Our extensive literature and database searches revealed 47 monogenic diseases associated with germline mutations in 24 out of 41 gene variant encoding for TGFβ components. Most of the TGFβ components are membrane or secretory proteins and they are therefore expected to pass through the endoplasmic reticulum (ER), where fidelity of proteins folding is stringently monitored via the ER quality control machineries. Elucidation of the molecular mechanisms of mutant proteins’ folding and trafficking showed the implication of ER associated protein degradation (ERAD) in the pathogenesis of some of the diseases. For example, hereditary hemorrhagic telangiectasia types 1 and 2 (HHT1 and HHT2) and familial pulmonary arterial hypertension (FPAH) associated with mutations in Endoglin, ALK1 and BMPR2 components of the signaling pathway, respectively, have all exhibited loss of function phenotype as a result of ER retention of some of their disease-causing variants. In some cases, this has led to premature protein degradation through the proteasomal pathway. We anticipate that ERAD will be involved in the mechanisms of other TGFβ signaling components and therefore warrants further research. In this review, we highlight advances in ER quality control mechanisms and their modulation as a potential therapeutic target in general with particular focus on prospect of their implementation in the treatment of monogenic diseases associated with TGFβ components including HHT1, HHT2, and PAH. In particular, we emphasis the need to establish disease mechanisms and to implement such novel approaches in modulating the molecular pathway of mutant TGFβ components in the quest for restoring protein folding and trafficking as a therapeutic approach.

Differential Expression of Circulating Plasma miRNA-370 and miRNA-10a from Patients with Hereditary Hemorrhagic Telangiectasia

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant, vascular disorder that presents with telangiectases and arteriovenous malformations. HHT is a genetically heterogeneous disorder, involving mutations in endoglin (ENG; HHT1) and activin receptor-like kinase 1 (ACVRL1/ALK1; HHT2) genes that account for over 85% of all HHT patients. The current diagnosis of HHT patients remains at the clinical level, but many suspected patients do not have a clear HHT diagnosis or do not show pathogenic mutations in HHT genes. This situation has prompted the search for biomarkers to help in the early diagnosis of the disease. We have analyzed the plasma levels in HHT patients of selected micro-RNAs (miRNAs), small single-stranded RNAs that regulate gene expression at the transcriptional level by interacting with specific RNA targets. A total of 16 HHT1 and 17 HHT2 plasma samples from clinically confirmed patients and 16 controls were analyzed in this study. Total RNA was purified from plasma, and three selected miRNAs (miRNA-10a, miRNA-214, and miRNA-370), related to the pathobiology of cardiovascular diseases and potentially targeting ENG or ALK1, were measured by quantitative polymerase chain reaction. Compared with controls, levels of miRNA-370, whose putative target is ENG, were significantly downregulated in HHT1, but not in HHT2, whereas the levels of miRNA-10a, whose putative target is ALK1, were significantly upregulated in HHT2, but not in HHT1. In addition, the levels of miRNA-214, potentially targeting ENG and ALK1, did not change in either HHT1 or HHT2 patients versus control samples. While further studies are warranted, these results suggest that dysregulated plasma levels of miRNA-370 or miRNA-10a could help to identify undiagnosed HHT1 or HHT2 patients, respectively.

[Hereditary hemorrhagic telangiectasia: a report of two cases]

This article reports two children with hereditary hemorrhagic telangiectasia (HHT). Patient 1 was a boy aged 12 years and was admitted due to intermittent cough and wheezing for more than 10 years. This boy and his mother and grandmother had a history of epistaxis. The boy had a history of the rupture of cerebral arteriovenous malformations. Gene detection showed a heterozygous mutation, c.277C>T(p.Arg93*), in the ENG gene. Patient 2 was a girl aged 13 years and was admitted due to cyanosis of lips for more than 1 year. The girl had a history of recurrent epistaxis and the manifestations of severe decline in pulmonary diffuse function, pulmonary hypertension, dilation of blood vessels at the distal end of lungs, and small arteriovenous communications in both lungs. Children with HHT often lack typical respiratory symptoms, which may lead to missed diagnosis and misdiagnosis in the early stage. Pulmonary computed tomography or right cardiac acoustic contrast can help with the diagnosis of HHT, and gene detection can improve the early diagnostic rate of this disease.

Bone morphogenetic protein receptors: Structure, function and targeting by selective small molecule kinase inhibitors

Bone morphogenetic proteins (BMPs) are secreted cytokines that control the fate and function of many different cell types. They exert their cellular responses via heteromeric complexes of specific BMP type I and type II serine/threonine kinase receptors, e.g. BMPRIA and BMPRII. Three type II and four type I receptors, also termed activin receptor-like kinases (ALKs), have been identified. The constitutively active type II kinase phosphorylates the type I receptor, which upon activation initiates intracellular signaling by phosphorylating SMAD effectors. Auxiliary cell surface receptors without intrinsic enzymatic motifs, such as Endoglin and Repulsive guidance molecules (RGM), can fine-tune signaling by regulating the interaction of the BMP ligands with the BMPRs. The functional annotation of the BMPR encoding genes has helped to understand underlying mechanisms of diseases in which these genes are mutated. Loss of function mutations in BMPRII, Endoglin or RGMc are causally linked to pulmonary arterial hypertension, hereditary hemorrhagic telangiectasia and juvenile hemochromatosis, respectively. In contrast, gain of function mutations in ACVR1, encoding ALK2, are linked to Fibrodysplasia ossificans progressiva and diffuse intrinsic pontine glioma. Here, we discuss BMPR identification, structure and function in health and disease. Moreover, we highlight the therapeutic promise of small chemical compounds that act as selective BMPR kinase inhibitors to normalize overactive BMPR signaling.

Hereditary hemorrhagic telangiectasia associated with cortical development malformation due to a start loss mutation in ENG

BACKGROUND

Hereditary hemorrhagic telangiectasia (HHT), also known as Rendu-Osler-Weber syndrome, is a rare disorder characterized by recurrent epistaxis, telangiectasias and systemic arteriovenous malformations (AVMs). HHT is associated with mutations in genes encoding for proteins involved in endothelial homeostasis such as ENG (endoglin) and ACVRL1 (activin receptor-like kinase-1).

CASE PRESENTATION

Here we describe a 22-year-old male presenting with a transient episode of slurred speech and left arm paresis. Brain MRI displayed polymicrogyria. A right-to-left shunt in absence of an atrial septum defect was noted. Chest CT revealed multiple pulmonary AVMs, likely causing paradoxical embolism manifesting as a transient ischemic attack. The heterozygous ENG variant, c.3G > A (p.Met1lle), was detected in the patient. This variant was also found in patient's mother and in his younger brother who displayed cortical dysplasia type 2.

CONCLUSIONS

The detection of cortical development malformations in multiple subjects from the same pedigree may expand the phenotypic features of ENG-related HHT patients. We suggest considering HHT in young patients presenting with acute cerebral ischemic events of unknown origin.

The Expression of Activin Receptor-Like Kinase 1 (ACVRL1/ALK1) in Hippocampal Arterioles Declines During Progression of Alzheimer's Disease

Cerebral amyloid angiopathy (CAA) in Alzheimer’s disease (AD)—deposition of beta amyloid (Aβ) within the walls of cerebral blood vessels—typically accompanies Aβ buildup in brain parenchyma and causes abnormalities in vessel structure and function. We recently demonstrated that the immunoreactivity of activin receptor-like kinase 1 (ALK1), the type I receptor for circulating BMP9/BMP10 (bone morphogenetic protein) signaling proteins, is reduced in advanced, but not early stages of AD in CA3 pyramidal neurons. Here we characterize vascular expression of ALK1 in the context of progressive AD pathology accompanied by amyloid angiopathy in postmortem hippocampi using immunohistochemical methods. Hippocampal arteriolar wall ALK1 signal intensity was 35% lower in AD patients (Braak and Braak Stages IV and V [BBIV-V]; clinical dementia rating [CDR1-2]) as compared with subjects with early AD pathologic changes but either cognitively intact or with minimal cognitive impairment (BBIII; CDR0-0.5). The intensity of Aβ signal in arteriolar walls was similar in all analyzed cases. These data suggest that, as demonstrated previously for specific neuronal populations, ALK1 expression in blood vessels is also vulnerable to the AD pathophysiologic process, perhaps related to CAA. However, cortical arterioles may remain responsive to the ALK1 ligands, such as BMP9 and BMP10 in early and moderate AD.

Deregulation of Drosha in the pathogenesis of hereditary hemorrhagic telangiectasia

PURPOSE OF REVIEW

The TGFβ (transforming growth factor β) superfamily - a large group of structurally related and evolutionarily conserved proteins - profoundly shapes and organizes the vasculature during normal development and adult homeostasis. Mutations inactivating several of its ligands, receptors, or signal transducers set off hereditary hemorrhagic telangiectasia (HHT), a disorder that causes capillary networks to form incorrectly. Drosha, an essential microRNA-processing enzyme, also interfaces with TGFβ signal transducers, but its involvement in vascular conditions had not been tested until recently. This review summarizes current evidence that links mutations of Drosha to HHT.

RECENT FINDINGS

Genetic studies have revealed that rare missense mutations in the Drosha gene occur more commonly among HHT patients than in healthy people. Molecular analyses also indicated that Drosha enzymes with HHT-associated mutations generate microRNAs less efficiently than their wild-type counterpart when stimulated by TGFβ ligands. In zebrafish or mouse, mutant Drosha proteins cause the formation of dilated, leaky blood vessels deprived of capillaries, similar to those typically found in patients with HHT.

SUMMARY

Recent evidence suggests that Drosha-mediated microRNA biogenesis contributes significantly to the control of vascular development and homeostasis by TGFβ. Loss or reduction of Drosha function may predispose carriers to HHT and possibly other vascular diseases.

Curaçao diagnostic criteria for hereditary hemorrhagic telangiectasia is highly predictive of a pathogenic variant in ENG or ACVRL1 (HHT1 and HHT2)

PURPOSE

Determine the variant detection rate for ENG, ACVRL1, and SMAD4 in individuals who meet consensus (Curaçao) criteria for the clinical diagnosis of hereditary hemorrhagic telangiectasia.

METHODS

Review of HHT center database for individuals with three or more HHT diagnostic criteria, in whom molecular genetic analysis for ENG, ACVRL1, and SMAD4 had been performed.

RESULTS

A variant known or suspected to be causal was detected in ENG in 67/152 (44.1%; 95% confidence interval [CI], 36.0-52.4%), ACVRL1 in 79/152 (52.0%; 95% CI, 43.7-60.1%), and SMAD4 in 2/152 (1.3%; 95% CI, 0.2-4.7%) family probands with definite HHT. Only 4/152 (2.6%; 95% CI, 0.7-6.6%) family probands did not have a variant in one of these genes.

CONCLUSION

Previous reports of the variant detection rate for ENG and ACVRL1 in HHT patients have come from laboratories, which receive samples from clinicians with a wide range of expertise in recognizing clinical manifestations of HHT. These studies suggest a significantly lower detection rate (~75-85%) than we have found in patients who meet strictly applied consensus criteria (96.1%). Analysis of SMAD4 adds an additional detection rate of 1.3%. HHT as defined by the Curaçao criteria is highly predictive of a causative variant in either ENG or ACVRL1.

Novel mutation in ENG gene causing Hereditary Hemorrhagic Telangiectasia in a Peruvian family

Hereditary Hemorrhagic Telangiectasia (HHT) is a rare disorder of vascular development. Common manifestations include epistaxis, telangiectasias and arteriovenous malformations (AVMs) in multiple organs. Most patients have deletions or missense mutations in the ENG or ACVRL1 gene respectively, significantly affecting endothelium homeostasis. We analyzed the ENG gene in five members of a Peruvian family affected by HHT. One novel mutation was found in exon four of the ENG gene c.408delA, at aminoacid residue 136. This mutation changes the subsequent reading frame producing an early stop at residue 162, preserving only one fourth of the normal protein of 658 aa. This mutation was found in the four affected members of family.

Gastrointestinal Bleeding in Patients with Hereditary Hemorrhagic Telangiectasia: Risk Factors and Endoscopic Findings

Background: We aimed to describe risk factors for gastrointestinal (GI) bleeding and endoscopic findings in patients with hereditary hemorrhagic telangiectasia (HHT). Methods: This is a prospective study from a referral HHT unit. Endoscopic tests were performed when there was suspicion of GI bleeding, and patients were divided as follows: with, without, and with unsuspected GI involvement. Results: 67 (27.9%) patients with, 28 (11.7%) patients without, and 145 (60.4%) with unsuspected GI involvement were included. Age, tobacco use, endoglin (ENG) mutation, and hemoglobin were associated with GI involvement. Telangiectases were mostly in the stomach and duodenum, but 18.5% of patients with normal esophagogastroduodenoscopy (EGD) had GI involvement in video capsule endoscopy (VCE). Telangiectases ≤ 3 mm and ≤10 per location were most common. Among patients with GI disease, those with hemoglobin < 8 g/dL or transfusion requirements (65.7%) were older and had higher epistaxis severity score (ESS) and larger telangiectases (>3 mm). After a mean follow-up of 34.2 months, patients with GI involvement required more transfusions and more emergency department and hospital admissions, with no differences in mortality. Conclusions: Risk factors for GI involvement have been identified. Patients with GI involvement and severe anemia had larger telangiectases and higher ESS. VCE should be considered in patients with suspicion of GI bleeding, even if EGD is normal.

SMAD4 Deficiency Leads to Development of Arteriovenous Malformations in Neonatal and Adult Mice

Background

Hereditary hemorrhagic telangiectasia (HHT) is a rare genetic vascular disorder caused by mutations in endoglin (ENG), activin receptor‐like kinase 1 (ACVRL1;ALK1), or SMAD4. Major clinical symptoms of HHT are arteriovenous malformations (AVMs) found in the brain, lungs, visceral organs, and mucosal surface. Animal models harboring mutations in Eng or Alk1 recapitulate all of these HHT clinical symptoms and have been useful resources for studying mechanisms and testing potential drugs. However, animal models representing SMAD4 mutations have been lacking. The goal of this study is to evaluate Smad4‐inducible knockout (iKO) mice as an animal model of HHT and compare the phenotypes with other established HHT animal models.

Methods and Results

Global Smad4 deletion was induced at neonatal and adult stages, and hemoglobin levels, gastrointestinal hemorrhage, and presence of aberrant arteriovenous connections were examined. Neonatal Smad4‐iKO mice exhibited signs of gastrointestinal bleeding and AVMs in the brain, intestine, nose, and retina. The radial expansion was decreased, and AVMs were detected on both distal and proximal retinal vasculature of Smad4‐iKOs. Aberrant smooth muscle actin staining was observed in the initial stage AVMs and their connecting veins, indicating abnormal arterial flow to veins. In adult mice, Smad4 deficiency caused gastrointestinal bleeding and AVMs along the gastrointestinal tract and wounded skin. HHT‐related phenotypes of Smad4‐iKOs appeared to be comparable with those found in Alk1‐iKO and Eng‐iKO mice.

Conclusions

These data further confirm that SMAD signaling is crucial for normal arteriovenous network formation, and Smad4‐iKO will be an alternative animal model of AVM research associated with HHT.