Hereditary haemorrhagic telangiectasia: mutation detection, test sensitivity and novel mutations

Case report: Early use of whole exome sequencing unveils HNRNPU-related neurodevelopmental disorder and answers additional clinical questions through reanalysis

This case report chronicles the diagnostic odyssey and resolution of a 27-year-old female with a complex neurodevelopmental disorder (NDD) using Whole Exome Sequencing (WES). The patient presented to a precision medicine clinic with multiple diagnoses including intellectual disability, autism spectrum disorder (ASD), obsessive-compulsive disorder (OCD), tics, seizures, and pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections (PANDAS). Although this patient previously had chromosomal microarray and several single-gene tests, the underlying cause of this patient's symptoms remained elusive. WES revealed a pathogenic missense mutation in the HNRNPU gene, associated with HNRNPU-related neurodevelopmental disorder (HNRNPU-NDD) and developmental and epileptic encephalopathy-54 (DEE54, OMIM: # 617391). Following this diagnoses, other treating clinicians identified additional indications for genetic testing, however, as the WES data was readily available, the clinical team was able to re-analyze the WES data to address their inquiries without requiring additional tests. This emphasizes the pivotal role of WES in expediting diagnoses, reducing costs, and providing ongoing clinical utility throughout a patient's life. Accessible WES data in primary care settings can enhance patient care by informing future genetic inquiries, enhancing coordination of care, and facilitating precision medicine interventions, thereby mitigating the burden on families and the healthcare system.

Endoglin mutants retained in the endoplasmic reticulum exacerbate loss of function in hereditary hemorrhagic telangiectasia type 1 (HHT1) by exerting dominant negative effects on the wild type allele

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant disorder affecting 1 in 5000-8000 individuals. Hereditary hemorrhagic telangiectasia type 1 (HHT1) is the most common HHT and manifests as diverse vascular malformations ranging from mild symptoms such as epistaxis and mucosal and cutaneous telangiectases to severe arteriovenous malformations (AVMs) in the lungs, brain or liver. HHT1 is caused by heterozygous mutations in the ENG gene, which encodes endoglin, the TGFβ homodimeric co-receptor. It was previously shown that some endoglin HHT1-causing variants failed to traffic to the plasma membrane due to their retention in the endoplasmic reticulum (ER) and consequent degradation by ER-associated degradation (ERAD). Endoglin is a homodimer formed in the ER, and we therefore hypothesized that mixed heterodimers might form between ER-retained variants and WT protein, thus hampering its maturation and trafficking to the plasma membrane causing dominant negative effects. Indeed, HA-tagged ER-retained mutants formed heterodimers with Myc-tagged WT endoglin. Moreover, variants L32R, V105D, P165L, I271N and C363Y adversely affected the trafficking of WT endoglin by reducing its maturation and plasma membrane localization. These results strongly suggest dominant negative effects exerted by these ER-retained variants aggravating endoglin loss of function in patients expressing them in the heterozygous state with the WT allele. Moreover, this study may help explain some of the variability observed among HHT1 patients due to the additional loss of function exerted by the dominant negative effects in addition to that due to haploinsufficiency. These findings might also have implications for some of the many conditions impacted by ERAD.

Hereditary hemorrhagic telangiectasia involving portal venous system: A case report and review of the literature

BACKGROUND

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant genetic disorder with an incidence of approximately 1 in 5000 in the general population. It is characterized by vasodilation, which affects specific organs, such as the skin, mucous membranes, brain, lungs, gastrointestinal tract, liver, and others. However, HHT rarely involves the portal venous system to cause serious clinical complications.

CASE SUMMARY

A 68-year-old woman was admitted to the emergency department due to four consecutive days of abdominal pain and bloody stool and was subsequently diagnosed with HHT. Computed tomography angiography confirmed the presence of an arteriovenous fistula (AVFs). Considering this specific manifestation, whole exome sequencing was performed. After a comprehensive evaluation, a selective superior mesenteric artery embolization was prioritized to avoid intestinal ischemia. The postoperative symptoms of the patient were quickly relieved. Unfortunately, two months post-procedure the patient died from intestinal necrosis and abdominal infection related to remaining AVFs.

CONCLUSION

For patients with diffuse superior mesenteric AVFs, selective mesenteric arterial embolization may lead to positive short-term outcomes.

uAUG creating variants in the 5'UTR of ENG causing Hereditary Hemorrhagic Telangiectasia

Hereditary Hemorrhagic Telangiectasia (HHT) is a rare, autosomal dominant, vascular disorder. About 80% of cases are caused by pathogenic variants in ACVRL1 (also known as ALK1) and ENG, with the remaining cases being unexplained. We identified two variants, c.-79C>T and c.-68G>A, in the 5'UTR of ENG in two unrelated patients. They create upstream AUGs at the origin of upstream overlapping open reading frames (uoORFs) ending at the same stop codon. To assess the pathogenicity of these variants, we performed functional assays based on the expression of wild-type and mutant constructs in human cells and evaluated their effect on ALK1 activity in a BMP-response element assay. This assay is mandatory for molecular diagnosis and has been so far only applied to coding ENG variants. These variants were associated with a decrease of protein levels in HeLa and HUVEC cells and a decreased ability to activate ALK1. We applied the same experiments on three additional uoORF-creating variants (c.-142A>T, c.-127C>T and c.-10C>T) located in the 5'UTR of ENG and previously reported in HHT patients. We found that all the analyzed variants alter protein levels and function. Additional experiments relying on an artificial deletion in our mutated constructs show that identified uAUGs could initiate the translation indicating that the associated effect is translation-dependent. Overall, we have identified two 5'UTR ENG variations in HHT patients and shed new light on the role of upstream ORFs on ENG regulation. Our findings contribute to the amelioration of molecular diagnosis in HHT.

Improving Hereditary Hemorrhagic Telangiectasia Molecular Diagnosis: A Referral Center Experience

BACKGROUND

Hereditary hemorrhagic telangiectasia (HHT) is a rare vascular disease inherited in an autosomal dominant manner. Disease-causing variants in endoglin (ENG) and activin A receptor type II-like 1 (ACVRL1) genes are detected in more than 90% of the patients undergoing molecular testing. The identification of variants of unknown significance is often seen as a challenge in clinical practice that makes family screening and genetic counseling difficult. Here, we show that the implementation of cDNA analysis to assess the effect of splice site variants on mRNA splicing is a powerful tool.

METHODS

Gene panel sequencing of genes associated with HHT and other arteriovenous malformation-related syndromes was performed. To evaluate the effect of the splice site variants, cDNA analysis of ENG and ACVRL1 genes was carried out.

RESULTS

three novel splice site variants were identified in ENG (c.68-2A > T and c.1311+4_1311+8del) and ACVLR1 (c.526-6C > G) genes correspondingly in three individuals with HHT that met ≥ 3 Curaçao criteria. All three variants led to an aberrant splicing inducing exon skipping (ENG:c.68-2A > T and ACVRL1:c.526-6C > G) or intron retention (ENG:c.1311+4_1311+8del) allowing the confirmation of the predicted effect on splicing and the reclassification from unknown significance to pathogenic/likely pathogenic of two of them.

CONCLUSIONS

RNA analysis should be performed to assess and/or confirm the impact of variants on splicing. The molecular diagnosis of HHT patients is crucial to allow family screening and accurate genetic counseling. A multidisciplinary approach including clinicians and geneticists is crucial when dealing with patients with rare diseases.

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.

A GDF2 missense mutation potentially involved in the pathogenesis of hereditary hemorrhagic telangiectasia: a case report

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant vascular disease. ENG and ACVRL1 gene variants account for up to 96% of all cases, while the remaining cases are caused by SMAD4 or GDF2 variants, or by currently undiscovered mutations in coding or non-coding regions. Here, we report a 47-year-old man who presented with duodenal bulb bleeding and chronic anemia. Physical examination also revealed bleeding from the skin and gingiva. His parents were cousins and one brother and one sister died in infancy from anemia and bleeding. Head computed tomography angiography (CTA) revealed a complete fetal posterior cerebral artery located in the left side, and pulmonary CTA showed pulmonary arterial hypertension. The patient was diagnosed with HHT. Peripheral blood was collected for whole-exome sequencing. Sequencing revealed a mutation in the GDF2 gene, which encodes bone morphogenetic protein-9 (BMP-9). The detected variant, c.352A > T(p.Ile118Phe), was predicted to be a neutral polymorphism; however, the patient's plasma BMP-9 levels were greatly reduced; we predicted that this might be caused by the GDF2 variant and might be involved in the HHT pathogenesis. Further research in cell lines and animal models is needed to verify the correlation between this GDF2 variant and the pathogenesis of HHT.

Brain arteriovenous malformation in hereditary hemorrhagic telangiectasia: Recent advances in cellular and molecular mechanisms

Hereditary hemorrhagic telangiectasia (HHT) is a genetic disorder characterized by vessel dilatation, such as telangiectasia in skin and mucosa and arteriovenous malformations (AVM) in internal organs such as the gastrointestinal tract, lungs, and brain. AVMs are fragile and tortuous vascular anomalies that directly connect arteries and veins, bypassing healthy capillaries. Mutations in transforming growth factor β (TGFβ) signaling pathway components, such as ENG (ENDOGLIN), ACVRL1 (ALK1), and SMAD4 (SMAD4) genes, account for most of HHT cases. 10-20% of HHT patients develop brain AVMs (bAVMs), which can lead to vessel wall rupture and intracranial hemorrhages. Though the main mutations are known, mechanisms leading to AVM formation are unclear, partially due to lack of animal models. Recent mouse models allowed significant advances in our understanding of AVMs. Endothelial-specific deletion of either Acvrl1, Eng or Smad4 is sufficient to induce AVMs, identifying endothelial cells (ECs) as primary targets of BMP signaling to promote vascular integrity. Loss of ALK1/ENG/SMAD4 signaling is associated with NOTCH signaling defects and abnormal arteriovenous EC differentiation. Moreover, cumulative evidence suggests that AVMs originate from venous ECs with defective flow-migration coupling and excessive proliferation. Mutant ECs show an increase of PI3K/AKT signaling and inhibitors of this signaling pathway rescue AVMs in HHT mouse models, revealing new therapeutic avenues. In this review, we will summarize recent advances and current knowledge of mechanisms controlling the pathogenesis of bAVMs, and discuss unresolved questions.

Combining genetic constraint with predictions of alternative splicing to prioritize deleterious splicing in rare disease studies

Background

Despite numerous molecular and computational advances, roughly half of patients with a rare disease remain undiagnosed after exome or genome sequencing. A particularly challenging barrier to diagnosis is identifying variants that cause deleterious alternative splicing at intronic or exonic loci outside of canonical donor or acceptor splice sites.

Results

Several existing tools predict the likelihood that a genetic variant causes alternative splicing. We sought to extend such methods by developing a new metric that aids in discerning whether a genetic variant leads to deleterious alternative splicing. Our metric combines genetic variation in the Genome Aggregate Database with alternative splicing predictions from SpliceAI to compare observed and expected levels of splice-altering genetic variation. We infer genic regions with significantly less splice-altering variation than expected to be constrained. The resulting model of regional splicing constraint captures differential splicing constraint across gene and exon categories, and the most constrained genic regions are enriched for pathogenic splice-altering variants. Building from this model, we developed ConSpliceML. This ensemble machine learning approach combines regional splicing constraint with multiple per-nucleotide alternative splicing scores to guide the prediction of deleterious splicing variants in protein-coding genes. ConSpliceML more accurately distinguishes deleterious and benign splicing variants than state-of-the-art splicing prediction methods, especially in “cryptic” splicing regions beyond canonical donor or acceptor splice sites.

Conclusion

Integrating a model of genetic constraint with annotations from existing alternative splicing tools allows ConSpliceML to prioritize potentially deleterious splice-altering variants in studies of rare human diseases.

Pulmonary Hypertension Associated Genetic Variants in Sarcoidosis Associated Pulmonary Hypertension

BACKGROUND

Pulmonary hypertension (PH) is a severe complication of sarcoidosis in a minority of patients. Several genetic defects are known to cause hereditary or sporadic PH, but whether variants in PH-associated genes are also involved in sarcoidosis-associated PH (SAPH) is unknown.

METHODS

40 patients with SAPH were individually matched to 40 sarcoidosis patients without PH (SA). Whole exome sequencing was performed to identify rare genetic variants in a diagnostic PH gene panel of 13 genes. Additionally, an exploratory analysis was performed to search for other genes of interest. From 572 genes biologically involved in PH pathways, genes were selected in which at least 15% of the SAPH patients and no more than 5% of patients without PH carried a rare variant.

RESULTS

In the diagnostic PH gene panel, 20 different rare variants, of which 18 cause an amino-acid substitution, were detected in 23 patients: 14 SAPH patients carried a variant, as compared to 5 SA patients without PH (p = 0.018). Most variants were of yet unknown significance. The exploratory approach yielded five genes of interest. First, the NOTCH3 gene that was previously linked to PH, and furthermore PDE6B, GUCY2F, COL5A1, and MMP21.

CONCLUSIONS

The increased frequency of variants in PH genes in SAPH suggests a mechanism whereby the presence of such a genetic variant in a patient may increase risk for the development of PH in the context of pulmonary sarcoidosis. Replication and studies into the functionality of the variants are required for further understanding the pathogenesis of SAPH.

An in vitro study on the effect of bevacizumab on endothelial cell proliferation and VEGF concentration level in patients with hereditary hemorrhagic telangiectasia

Previous studies have demonstrated that vascular endothelial growth factor (VEGF) is upregulated in patients with hereditary hemorrhagic telangiectasia (HHT). The use of Bevacizumab as an anti-angiogenic treatment agent seems promising. The purpose of the present in vitro study was to determine the efficacy and potential toxicity levels of bevacizumab on cell proliferation and VEGF concentrations in endothelial cells of HHT patients. In this in vitro study, endothelial cells from patients with HHT and HUVECs (control) were incubated with different concentration levels of bevacizumab (2, 4, 6, 8 or 10 mg/ml). After 24, 48 or 72 h, the cell proliferation was assessed by Alamar Blue^® Assay and the VEGF levels in the cell culture supernatants were measured by VEGF-ELISA. All endothelial cells incubated with bevacizumab showed an initial decrease in cell proliferation. Cell proliferation recovered within 72 h in cell cultures incubated with concentration levels of up to 4 mg/ml bevacizumab, whereas those incubated with higher concentration levels showed a continuous decline in cell proliferation. VEGF expression decreased after 24 h in cell cultures incubated with bevacizumab concentration levels of 2 and 4 mg/ml but increased again after 48 h. Cell cultures incubated with bevacizumab concentration levels of 10 mg/ml showed a constant decline in VEGF expression without any tendency for recovery. Translating these results into daily clinical practice, the present study suggests that the intranasal submucosal injection of bevacizumab in HHT patients should not exceed a concentration level of 4 mg/ml. Overall, higher bevacizumab concentration levels not only reduce VEGF expression but pose a higher risk of toxic effects on endothelial cells as they jeopardize cell proliferation.

[Hereditary hemorrhagic telangiectasia (Rendu-Osler syndrome)]

The analysis of publications is carried out and current data concerning the etiology, pathogenesis, diagnosis, and principles of treatment of hereditary hemorrhagic telangiectasia are presented.

Imaging to intervention: a review of what the Interventionalist needs to Know about Hereditary Hemorrhagic Telangiectasia

Hereditary hemorrhagic telangiectasia (HHT) is a disorder that affects 1 in 5000-10,000 people worldwide and can result in devastating complications such as cerebral abscess, stroke, massive hemorrhage, and even death. HHT is an autosomal dominant disorder that leads to the formation of abnormal communication between the arteries and veins with a resultant spectrum of vascular anomalies. The disorder affects many organ systems and thus requires a dedicated multidisciplinary approach. Interventional radiologists are vital members of this team providing expertise not only in disease management, but in complex embolotherapy, helping to maintain the health of these patients. This article reviews clinical manifestations, screening guidelines, diagnostic criteria, and endovascular management of HHT.

Clinical manifestations of patients with GDF2 mutations associated with hereditary hemorrhagic telangiectasia type 5

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant fibrovascular dysplasia caused by mutations in ENG, ACVRL1, and SMAD4. Increasingly, there has been an appreciation for vascular conditions with phenotypic overlap to HHT but which have distinct clinical manifestations and arise from novel or uncharacterized gene variants. This study reported on a cohort of four unrelated probands who were diagnosed with a rare form of GDF2-related HHT5, for which only five prior cases have been described. Two patients harbored heterozygous missense variants not previously annotated as pathogenic (p.Val403Ile; p.Glu355Gln). Clinically, these patients had features resembling HHT1, including cerebrovascular involvement of their disease (first report documenting cerebral involvement of HHT5), but with earlier onset of epistaxis and a unique anatomic distribution of dermal capillary lesions that involved the upper forelimbs, trunk, and head. The other two patients harbored interstitial deletions larger than five megabases between 10q11.22 and 10q11.23 that included GDF2. To our knowledge, this is the first report detailing large genomic deletions leading to HHT5. These patients also demonstrated mucocutaneous capillary dysplasias, including intranasal vascular lesions complicated by childhood-onset epistasis, with a number of extravascular findings related to their 10q11.21q11.23 deletion. In conclusion, patients with GDF2-related HHT may present with a number of unique characteristics that differ from classically reported features of HHT.

TGFβ-Neurotrophin Interactions in Heart, Retina, and Brain

Ischemic insults to the heart and brain, i.e., myocardial and cerebral infarction, respectively, are amongst the leading causes of death worldwide. While there are therapeutic options to allow reperfusion of ischemic myocardial and brain tissue by reopening obstructed vessels, mitigating primary tissue damage, post-infarction inflammation and tissue remodeling can lead to secondary tissue damage. Similarly, ischemia in retinal tissue is the driving force in the progression of neovascular eye diseases such as diabetic retinopathy (DR) and age-related macular degeneration (AMD), which eventually lead to functional blindness, if left untreated. Intriguingly, the easily observable retinal blood vessels can be used as a window to the heart and brain to allow judgement of microvascular damages in diseases such as diabetes or hypertension. The complex neuronal and endocrine interactions between heart, retina and brain have also been appreciated in myocardial infarction, ischemic stroke, and retinal diseases. To describe the intimate relationship between the individual tissues, we use the terms heart-brain and brain-retina axis in this review and focus on the role of transforming growth factor β (TGFβ) and neurotrophins in regulation of these axes under physiologic and pathologic conditions. Moreover, we particularly discuss their roles in inflammation and repair following ischemic/neovascular insults. As there is evidence that TGFβ signaling has the potential to regulate expression of neurotrophins, it is tempting to speculate, and is discussed here, that cross-talk between TGFβ and neurotrophin signaling protects cells from harmful and/or damaging events in the heart, retina, and brain.

Pilot investigation of circulating angiogenic and inflammatory biomarkers associated with vascular malformations

Background

Vascular malformations in the central nervous system are difficult to monitor and treat due to their inaccessible location. Angiogenic and inflammatory proteins are secreted into the bloodstream and may serve as useful biomarkers for identifying patients at risk for complications or with certain disease phenotypes.

Methods

A validated multiplex protein array consisting of 26 angiogenic and inflammatory biomarkers (Angiome) was assessed in plasma isolated from healthy controls and patients with either sporadic brain arteriovenous malformation (BAVM), familial cerebral cavernous malformation (CCM), or hereditary hemorrhagic telangiectasia (HHT). These samples were obtained from archives of ongoing research studies at the University of California San Francisco and through prospective collection at the Toronto HHT Centre at St. Michael’s Hospital.

Results

We compared circulating biomarker levels from each patient group to healthy controls and analyzed each pairwise combination of patient groups for differences in biomarker levels. Additionally, we analyzed the HHT samples to determine the association between biomarker levels and the following HHT-specific phenotypes, BAVM, pulmonary arteriovenous malformation (PAVM), liver vascular malformation (LVM), and gastrointestinal (GI) bleeding. Compared to controls, levels of SDF1 were significantly elevated in HHT patients (Proportional Increase [PI] = 1.87, p < 0.001, q = 0.011). Levels of sENG were significantly reduced in HHT patients compared to controls (PI = 0.56, p < 0.001, q < 0.001), reflecting the prevalence of HHT1 patients in this cohort. Levels of IL6 (PI = 3.22, p < 0.001, q < 0.001) and sTGFβR3 (PI = 0.70, p = 0.001, q < 0.029) differed significantly in CCM patients compared to controls. Compared to controls, ten of the biomarkers were significantly different in sporadic BAVM patients (q-values < 0.05). Among the pairwise combinations of patient groups, a significant elevation was observed in TGFβ1 in CCM patients compared to sporadic BAVM patients (PI = 2.30, p < 0.001, q = 0.034). When examining the association of circulating biomarker levels with HHT-specific phenotypes, four markers were significantly lower in HHT patients with BAVM (q-values < 0.05), and four markers were significantly higher in patients with LVM (q-values < 0.05).

Conclusions

This pilot study suggests that the profile of circulating angiogenic and inflammatory biomarkers may be unique to each type of vascular malformation. Furthermore, this study indicates that circulating biomarkers may be useful for assessing phenotypic traits of vascular malformations.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-021-02009-7.

Endoglin deficiency impairs VEGFR2 but not FGFR1 or TIE2 activation and alters VEGF-mediated cellular responses in human primary endothelial cells

Hereditary hemorrhagic telangiectasia (HHT) is a genetic disease characterized by vascular dysplasia. Mutations of the endoglin (ENG) gene that encodes a co-receptor of the transforming growth factor β1 signaling pathway cause type I HHT. ENG is primarily expressed in endothelial cells (ECs), but its interaction with other key angiogenic pathways to control angiogenesis has not been well addressed. The aim of this study is to investigate ENG interplay with VEGFR2, FGFR1 and TIE2 in primary human ECs. ENG was knocked-down with siRNA in human umbilical vein ECs (HUVECs) and human lung microvascular ECs (HMVEC-L). Gene expression was measured by RT-qPCR and Western blotting. Cell signaling pathway activation was analyzed by detecting phosphor-ERK and phosphor-AKT levels. Cell migration and apoptosis were assessed using the Boyden chamber assay and the CCK-8 Kit, respectively. Loss of ENG in HUVECs led to significantly reduced expression of VEGFR2 but not TIE2 or FGFR1, which was also confirmed in HMVEC-L. HUVECs lacking ENG had significantly lower levels of active Rac1 and a substantial reduction of the transcription factor Sp1, an activator of VEGFR2 transcription, in nuclei. Furthermore, VEGF- but not bFGF- or angiopoietin-1-induced phosphor-ERK and phosphor-AKT were suppressed in ENG deficient HUVECs. Functional analysis revealed that ENG knockdown inhibited cell migratory but enhanced anti-apoptotic activity induced by VEGF. In contrast, bFGF, angiopoietin-1 and -2 induced HUVEC migration and anti-apoptotic activities were not affected by ENG knockdown. In conclusion, ENG deficiency alters the VEGF/VEGFR2 pathway, which may play a role in HHT pathogenesis.

Genetic counseling and testing for hereditary hemorrhagic telangiectasia

Genetic counseling is an important means of identifying a patient's genetic risk of hereditary hemorrhagic telangiectasia (HHT) and assisting patients in making informed decisions about their health. With an increase in understanding of the genetic mechanisms underlying HHT over the last decade, genetic counseling is increasingly being incorporated into the care of patients affected by HHT. In addition to refining the diagnosis of symptomatic patients, genetic testing can help to distinguish asymptomatic, at-risk patients from those who are unaffected by HHT. The purpose of this review article is to summarize the current knowledge regarding the role of genetic counseling and genetic testing in identifying and managing HHT in at-risk populations. This article also reviews the guidelines, outcomes, risks, and challenges of genetic counseling and testing for HHT in various patient populations, and provides an algorithm for the use of genetic counseling in symptomatic and asymptomatic patients.

Hereditary haemorrhagic telangiectasia: A case report

Background

Hereditary haemorrhagic telangiectasia is an autosomal dominant genetic disorder characterized by abnormalities in blood vessel formation. The clinical manifestations of patients affected with hereditary haemorrhagic telangiectasia include mucocutaneous telangiectasias and visceral arteriovenous malformations.

Case Summary

We report the case of a 30-year-old female diagnosed with hereditary haemorrhagic telangiectasia presenting with the classic triad of recurrent epistaxis, mucocutaneous telangiectasias and family history of hereditary haemorrhagic telangiectasia with activin receptor-like kinase 1 mutation. Upon skin examination, she was noted to have telangiectasias under left naris, inner lower lip and surface of the tongue, and a vascular malformation on the right forearm.

Conclusion

Although the skin involvement and epistaxis may be mild symptoms and signs of hereditary haemorrhagic telangiectasia, timely recognition of these can ensure vigilant monitoring of potential severe complications from cerebral and pulmonary visceral arteriovenous malformations.

Applicability of Transthoracic Contrast Echocardiography for the Diagnosis and Treatment of Idiopathic Pulmonary Arteriovenous Malformations

Objective: To explore the preferred test to screen for pulmonary arteriovenous malformations (PAVMs) and to predict the probability of interventional embolization. Methods: We performed a retrospective observational study evaluating patients with idiopathic PAVMs from 2009 to 2019. After clinical evaluation, a total of 105 patients were studied, including 71 patients with positive digital subtraction pulmonary angiography (DSPA) findings and 34 with negative DSPA findings. The following patient data were assessed: blood test, chest radiograph, transthoracic contrast echocardiography (TTCE), and DSPA findings. Results: The majority of patients with idiopathic PAVMs were female (66.2% with positive DSPA findings). We found a good κ-coefficient of 0.77 with strong consistency for inter observer agreement concerning the pulmonary right-to-left shunt (RLS) grade on TTCE, which was superior to conventional chest radiographs. The positive predictive value (PPV) of the radiographic features for PAVMs on DSPA was 0.83 (95% CI 0.64-1.0) and 0.44 for the possibility of embolization (95% CI 0.19-0.70). The PPV of the shunt grade of PAVMs on DSPA was 0.14 (95% CI 0.01-0.29) for grade 1, 0.74 (95% CI 0.60-0.88) for grade 2, and 0.97 (95% CI 0.92-1.0) for grade 3. The PPVs of pulmonary shunt grades 2 and 3 on TTCE for the possibility of embolization for PAVMs were 0.21 (95% CI, 0.05-0.36) and 0.87 (95% CI, 0.79-0.99), respectively. Conclusion: TTCE is the preferred screening test for PAVMs. The pulmonary RLS grade on TTCE not only identifies the likelihood of PAVMs but also predicts the probability for embolization.

Identifying Potential Mutations Responsible for Cases of Pulmonary Arterial Hypertension

Pulmonary Arterial Hypertension (PAH) is a progressive and devastating disease for which there is an escalating body of genetic and related pathophysiological information on disease pathobiology. Nevertheless, the success to date in identifying susceptibility genes, genetic variants and epigenetic processes has been limited due to PAH clinical multi-faceted variations. A number of germline gene candidates have been proposed but demonstrating consistently the association with PAH has been problematic, at least partly due to the reduced penetrance and variable expressivity. Although the data for bone morphogenetic protein receptor type 2 (BMPR2) and related genes remains undoubtedly the most extensive, recent advanced gene sequencing technologies have facilitated the discovery of further gene candidates with mutations among those with and without familial forms of PAH. An in depth understanding of the multitude of biologic variations associated with PAH may provide novel opportunities for therapeutic intervention in the coming years. This knowledge will irrevocably provide the opportunity for improved patient and family counseling as well as improved PAH diagnosis, risk assessment, and personalized treatment.

Ocular lesions in hereditary hemorrhagic telangiectasia: genetics and clinical characteristics

Background

The aim of our study is to study the association between eye lesions in Hereditary Hemorrhagic Telangiectasia (HHT) and other signs of the disease, as well as to characterize its genetics.

Methods

A cross-sectional study was conducted of a cohort of 206 patients studied in the HHT Unit of Hospital de Sierrallana, a reference centre for Spanish patients with HHT. Odds ratios for several symptoms or characteristics of HHT and ocular lesions were estimated using logistic regression adjusting for age and sex.

Results

The ocular involvement was associated with being a carrier of a mutation for the ENG gene, that is, suffering from a type 1 HHT involvement (OR = 2.09; 95% CI [1.17–3.72]). p = 0.012). In contrast, patients with ocular lesions have less frequently mutated ACVRL1/ALK1 gene (OR = 0.52; 95% CI [0.30–3.88], p = 0.022).

Conclusions

In conclusion, half of the patients with HHT in our study have ocular involvement. These eye lesions are associated with mutations in the ENG gene and ACVRL1/ALK1 gene. Thus, the ENG gene increases the risk of ocular lesions, while being a carrier of the mutated ACVRL1/ALK1 gene decreases said risk.

Extracranial arteriovenous malformations: from bedside to bench

Arteriovenous malformation (AVM) is defined as a fast-flow vascular anomaly that shunts blood from arteries directly to veins. This short circuit of blood flow contributes to progressive expansion of draining veins, resulting in ischaemia, tissue deformation and in some severe cases, congestive heart failure. Various medical interventions have been employed to treat AVM, however, management of which remains a huge challenge because of its high recurrence rate and lethal complications. Thus, understanding the underlying mechanisms of AVM development and progression will help direct discovery and a potential cure. Here, we summarize current findings in the field of extracranial AVMs with the aim to provide insight into their aetiology and molecular influences, in the hope to pave the way for future treatment.

Current HHT genetic overview in Spain and its phenotypic correlation: data from RiHHTa registry

BACKGROUND

Hereditary hemorrhagic telangiectasia (HHT) is a rare vascular disease with autosomal dominant inheritance. Disease-causing variants in endoglin (ENG) and activin A receptor type II-like 1 (ACVRL1) genes are detected in more than 90% of cases submitted to molecular diagnosis.

METHODS

We used data from the RiHHTa (Computerized Registry of Hereditary Hemorrhagic Telangiectasia) registry to describe genetic variants and to assess their genotype-phenotype correlation among HHT patients in Spain.

RESULTS

By May 2019, 215 patients were included in the RiHHTa registry with a mean age of 52.5 ± 16.5 years and 136 (63.3%) were women. Definitive HHT diagnosis defined by the Curaçao criteria were met by 172 (80%) patients. Among 113 patients with genetic test, 77 (68.1%) showed a genetic variant in ACVRL1 and 36 (31.8%) in ENG gene. The identified genetic variants in ACVRL1 and ENG genes and their clinical significance are provided. ACVRL1 mutations were more frequently nonsense (50%) while ENG mutations were more frequently, frameshift (39.1%). ENG patients were significantly younger at diagnosis (36.9 vs 45.7 years) and had pulmonary arteriovenous malformations (AVMs) (71.4% vs 24.4%) and cerebral AVMs (17.6% vs 2%) more often than patients with ACVRL1 variants. Patients with ACVRL1 variants had a higher cardiac index (2.62 vs 3.46), higher levels of hepatic functional blood tests, and anemia (28.5% vs 56.7%) more often than ENG patients.

CONCLUSIONS

ACVRL1 variants are more frequent than ENG in Spain. ACVRL1 patients developed symptomatic liver disease and anemia more often than ENG patients. Compared to ACVRL1, those with ENG variants are younger at diagnosis and show pulmonary and cerebral AVMs more frequently.

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.

Gender differences in hereditary hemorrhagic telangiectasia severity

Background

Gender differences in organ involvement and clinical severity have been poorly described in hereditary hemorrhagic telangiectasia (HHT). The aim of this study was to describe differences in the severity of HHT manifestations according to gender.

Methods

Severity was measured according to Epistaxis Severity Score (ESS), Simple Clinical Scoring Index for hepatic involvement, a general HHT-score, needing for invasive treatment (pulmonary or brain arteriovenous malformations -AVMs- embolization, liver transplantation or Young’s surgery) or the presence of adverse outcomes (severe anemia, emergency department -ED- or hospital admissions and mortality).

Results

One hundred forty-two (58.7%) women and 100 (41.3%) men were included with a mean age of 48.9 ± 16.6 and 49 ± 16.5 years, respectively. Women presented hepatic manifestations (7.1% vs 0%) and hepatic involvement (59.8% vs 47%), hepatic AVMs (28.2% vs 13%) and bile duct dilatation (4.9% vs 0%) at abdominal CT, and pulmonary AVMs at thoracic CT (35.2% vs 23%) more often than men. The Simple Clinical Scoring Index was higher in women (3.38 ± 1.2 vs 2.03 ± 1.2), and more men were considered at low risk of harboring clinically significant liver disease than women (61% vs 25.3%). These differences were mantained when considering HHT1 and HHT2 patients separetely. Duodenal telangiectasia were more frequent in men than women (21% vs 9.8%). Invasive treatments were more frequently needed in women (28.2% vs 16%) but men needed attention at the ED more often than women (48% vs 28.2%), with no differences in ESS, HHT-score, anemia hospital admissions or mortality.

Conclusions

HHT women showed more severe hepatic involvement than men, also among HHT1 and HHT2 patients. Women had higher prevalence of pulmonary AVMs and needed invasive procedures more frequently, while men needed attention at the ED more often. These data might help physicians to individualize HHT patients follow-up.

Elevated endothelial Sox2 causes lumen disruption and cerebral arteriovenous malformations

Lumen integrity in vascularization requires fully differentiated endothelial cells (ECs). Here, we report that endothelial-mesenchymal transitions (EndMTs) emerged in ECs of cerebral arteriovenous malformation (AVMs) and caused disruption of the lumen or lumen disorder. We show that excessive Sry-box 2 (Sox2) signaling was responsible for the EndMTs in cerebral AVMs. EC-specific suppression of Sox2 normalized endothelial differentiation and lumen formation and improved the cerebral AVMs. Epigenetic studies showed that induction of Sox2 altered the cerebral-endothelial transcriptional landscape and identified jumonji domain-containing protein 5 (JMJD5) as a direct target of Sox2. Sox2 interacted with JMJD5 to induce EndMTs in cerebral ECs. Furthermore, we utilized a high-throughput system to identify the β-adrenergic antagonist pronethalol as an inhibitor of Sox2 expression. Treatment with pronethalol stabilized endothelial differentiation and lumen formation, which limited the cerebral AVMs.

Characterization of a mutation in the zona pellucida module of Endoglin that causes Hereditary Hemorrhagic Telangiectasia

Hereditary hemorrhagic telangiectasia (HHT) is a vascular rare disease characterized by nose and gastrointestinal bleeding, skin and mucosa telangiectasias, and arteriovenous malformations in internal organs. HHT shows an autosomal dominant inheritance and a worldwide prevalence of approximately 1:5000 individuals. In >80% of patients, HHT is caused by mutations in either ENG (HHT1) or ACVRL1 (HHT2) genes, which code for the membrane proteins Endoglin and Activin A Receptor Type II-Like Kinase 1 (ALK1), respectively, both belonging to the TGF-β/BMP signaling pathway. In this work, we describe a novel mutation in exon 9 of ENG (c.1145 G > A) found in five affected members of a family, all of them with characteristic symptoms of HHT. This mutation involves Cys382 residue of the Endoglin protein (p.Cys382 > Tyr) in the zona pellucida (ZP) module of its extracellular region. This is a critical residue involved in a conserved intrachain disulphide bond and in the correct folding of the protein. In fact, transfection studies in human cells using Endoglin expression vectors demonstrated that the p.Cys382 > Tyr mutation results in a marked reduction in the levels of the Endoglin protein. These results demonstrate the pathogenic role for this variant in HHT1 and confirm the key function of Cys382 in Endoglin expression.

Systematic screening in hereditary hemorrhagic telangiectasia: a review

PURPOSE OF REVIEW

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant inherited disease characterized by telangiectasia and arteriovenous malformations (AVMs). To date, five genetic types of HHT and one combined juvenile polyposis syndrome and HHT are known. Clinical and genetic screening of patients suspected with HHT is recommended to confirm the diagnosis and to prevent complications associated with HHT. The aim of this article is to give an overview of the evidence and to formulate a recommendation for clinicians concerning screening for HHT.

RECENT FINDINGS

Complications of HHT such as stroke, brain abscess and intracranial hemorrhage are caused by pulmonary and cerebral AVMs (CAVMs) and can often be prevented by screening and treatment when possible. Screening and treatment of these AVMs will result in an increased life expectancy comparable with that of the general population as opposed to unscreened and untreated HHT patients.

SUMMARY

Screening of HHT patients and their first-degree relatives is recommended to prevent severe complications including stroke, brain abscess and intracranial hemorrhage.

Characterization of a family mutation in the 5' untranslated region of the endoglin gene causative of hereditary hemorrhagic telangiectasia

Hereditary hemorrhagic telangiectasia (HHT) is a vascular disease characterized by nose and gastrointestinal bleeding, telangiectases in skin and mucosa, and arteriovenous malformations in major internal organs. Most patients carry a mutation in the coding region of the endoglin (ENG) or activin A receptor type II-1 (ACVRL1) gene. Nonetheless, in around 15% of patients, sequencing analysis and duplication/deletion tests fail to pinpoint mutations in the coding regions of these genes. In these cases, it has been shown that sequencing of the 5’-untranslated region (5’UTR) of ENG may be useful to identify novel mutations in the ENG non-coding region. Here we report the genetic characterization and functional analysis of the heterozygous mutation c.-142A>T in the 5’UTR region of ENG found in a family with several members affected by HHT. This variant gives rise to a new initiation codon of the protein that involves the change in its open reading frame. Transfection studies in monkey cells using endoglin expression vectors demonstrated that c-142A>T mutation results in a clear reduction in the levels of the endoglin protein. These results support the inclusion of the 5’UTR of ENG in the standard genetic testing for HHT to increase its sensitivity.

Hereditary hemorrhagic telangiectasia and pulmonary arteriovenous malformations: clinical aspects

Hereditary hemorrhagic telangiectasia (HHT) is a genetic disorder of blood vessel formation resulting in mucocutaneous telangiectasias and visceral arteriovenous malformations. Nearly half of patients with HHT will have pulmonary arteriovenous malformations (PAVM) that place them at risk for potentially fatal complications that can occur when blood bypasses the pulmonary capillary circulation or as a result of PAVM rupture. Other manifestations of HHT outside the lung may increase the rate and severity of PAVM complications, creating unique clinical challenges. Management hinges on timely screening and diagnosis, followed by treatment of amenable PAVMs with transcatheter embolization in conjunction with medical management and prophylactic measures to treat and prevent complications. The purpose of this review is to highlight the clinical manifestations of PAVMs specific to patients with HHT and to detail screening and treatment strategies that can reduce the risk of developing life-threatening complications.

Hereditary hemorrhagic telangiectasia: diagnosis and management from the hematologist's perspective

Hereditary hemorrhagic telangiectasia (HHT), also known as Osler-Weber-Rendu syndrome, is an autosomal dominant disorder that causes abnormal blood vessel formation. The diagnosis of hereditary hemorrhagic telangiectasia is clinical, based on the Curaçao criteria. Genetic mutations that have been identified include ENG, ACVRL1/ALK1, and MADH4/SMAD4, among others. Patients with HHT may have telangiectasias and arteriovenous malformations in various organs and suffer from many complications including bleeding, anemia, iron deficiency, and high-output heart failure. Families with the same mutation exhibit considerable phenotypic variation. Optimal treatment is best delivered via a multidisciplinary approach with appropriate diagnosis, screening and local and/or systemic management of lesions. Anti-angiogenic agents such as bevacizumab have emerged as a promising systemic therapy in reducing bleeding complications but are not curative. Other pharmacological agents include iron supplementation, antifibrinolytics and hormonal treatment. This review discusses the biology of HHT, management issues that face the practising hematologist, and considerations of future directions in HHT treatment.

Differential diagnosis of hepatopulmonary syndrome (HPS): Portopulmonary hypertension (PPH) and hereditary hemorrhagic telangiectasia (HHT)

Hepatopulmonary syndrome (HPS) is a severe complication of advanced liver disease associated with an extremely poor prognosis. HPS is diagnosed in 4-47% of patients with cirrhosis and in 15-20% of candidates for liver transplantation. In addition, severe hypoxia is associated with a high risk of complications of liver transplantation (a 30% chance during the first 90 days) and increases the gap between transplantation and improving arterial oxygenation. The pathogenesis of HPS is not fully understood, and no effective pharmacological treatment has been developed yet. Currently, the treatment of choice for HPS is orthotopic liver transplantation. Non-specific clinical criteria and the lack of standardized diagnostic criteria for determining HPS can lead to diagnostic errors. Portopulmonary hypertension and hereditary hemorrhagic telangiectasia, also known as Osler-Weber-Rendu syndrome, are pulmonary complications of liver disease which should be differentially diagnosed from HPS.

The role of genetics in pulmonary arterial hypertension

Group 1 pulmonary hypertension or pulmonary arterial hypertension (PAH) is a rare disease characterized by proliferation and occlusion of small pulmonary arterioles, leading to progressive elevation of pulmonary artery pressure and pulmonary vascular resistance, and right ventricular failure. Historically, it has been associated with a high mortality rate, although, over the last decade, treatment has improved survival. PAH includes idiopathic PAH (IPAH), heritable PAH (HPAH), and PAH associated with certain medical conditions. The aetiology of PAH is heterogeneous, and genetics play an important role in some cases. Mutations in BMPR2, encoding bone morphogenetic protein receptor 2, a member of the transforming growth factor-β superfamily of receptors, have been identified in 70% of cases of HPAH, and in 10-40% of cases of IPAH. Other genetic causes of PAH include mutations in the genes encoding activin receptor-like type 1, endoglin, SMAD9, caveolin 1, and potassium two-pore-domain channel subfamily K member 3. Mutations in the gene encoding T-box 4 have been identified in 10-30% of paediatric PAH patients, but rarely in adults with PAH. PAH in children is much more heterogeneous than in adults, and can be associated with several genetic syndromes, congenital heart disease, pulmonary disease, and vascular disease. In addition to rare mutations as a monogenic cause of HPAH, common variants in the gene encoding cerebellin 2 increase the risk of PAH by approximately two-fold. A PAH panel of genes is available for clinical testing, and should be considered for use in clinical management, especially for patients with a family history of PAH. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Hereditary Hemorrhagic Telangiectasia

Hereditary hemorrhagic telangiectasia (HHT) is an underrecognized and underdiagnosed autosomal-dominant angiodysplasia that has an estimated prevalence of 1 in 5000 individuals, with variable clinical presentations even within family members with identical mutations. The most common manifestations are telangiectasias of the skin and nasal mucosa. However, HHT can often be complicated by the presence of arteriovenous malformations and telangiectasias in the lungs, brain, gastrointestinal tract, and liver that are often silent and can lead to life-threatening complications of stroke and hemorrhage. This article reviews HHT for the pulmonologist, who is not uncommonly the first practitioner to encounter these patients.

Smad4 Deficiency in Smooth Muscle Cells Initiates the Formation of Aortic Aneurysm

RATIONALE

Aortic aneurysm is a life-threatening cardiovascular disorder caused by the predisposition for dissection and rupture. Genetic studies have proved the involvement of the transforming growth factor-β (TGF-β) pathway in aortic aneurysm. Smad4 is the central mediator of the canonical TGF-β signaling pathway. However, the exact role of Smad4 in smooth muscle cells (SMCs) leading to the pathogenesis of aortic aneurysms is largely unknown.

OBJECTIVE

To determine the role of smooth muscle Smad4 in the pathogenesis of aortic aneurysms.

METHODS AND RESULTS

Conditional gene knockout strategy combined with histology and expression analysis showed that Smad4 or TGF-β receptor type II deficiency in SMCs led to the occurrence of aortic aneurysms along with an upregulation of cathepsin S and matrix metallopeptidase-12, which are proteases essential for elastin degradation. We further demonstrated a previously unknown downregulation of matrix metallopeptidase-12 by TGF-β in the aortic SMCs, which is largely abrogated in the absence of Smad4. Chemotactic assay and pharmacologic treatment demonstrated that Smad4-deficient SMCs directly triggered aortic wall inflammation via the excessive production of chemokines to recruit macrophages. Monocyte/macrophage depletion or blocking selective chemokine axis largely abrogated the progression of aortic aneurysm caused by Smad4 deficiency in SMCs.

CONCLUSIONS

The findings reveal that Smad4-dependent TGF-β signaling in SMCs protects against aortic aneurysm formation and dissection. The data also suggest important implications for novel therapeutic strategies to limit the progression of the aneurysm resulting from TGF-β signaling loss-of-function mutations.

Pulmonary vascular complications of hereditary haemorrhagic telangiectasia

PURPOSE OF REVIEW

The purpose of this study is to present the latest advances and recommendations in the diagnosis and treatment of pulmonary vascular complications associated with hereditary haemorrhagic telangiectasia (HHT): pulmonary arteriovenous malformations (PAVMs), pulmonary arterial hypertension (PAH), pulmonary hypertension associated with high output cardiac failure or liver vascular malformations, haemoptysis, haemothorax and thromboembolic disease.

RECENT FINDINGS

Transthoracic contrast echocardiography has been validated as a screening tool for PAVM in patients with suspected HHT. Advancements in genetic testing support its use in family members at risk as a cost-effective measure. Therapy with bevacizumab in patients with high output cardiac failure and severe liver AVMs showed promising results. PAH tends to be more aggressive in HHT type 2 patients.

SUMMARY

Patients suffering from this elusive disease should be referred to HHT specialized centres to ensure a standardized and timely approach to diagnosis and management.

How to manage patients with hereditary haemorrhagic telangiectasia

Hereditary haemorrhagic telangiectasia is a rare systemic autosomal dominantly inherited disorder of the fibrovascular tissue with a wide variety of clinical manifestations. Diagnosis is based on the clinical Curaçao criteria or molecular genetic testing. Dilated vessels can develop into telangiectases or larger vascular malformations in various organs, calling for an interdisciplinary approach. Epistaxis and gastrointestinal bleeding can result from these vascular defects. Various conservative and interventional treatments have been described for these conditions. However, no optimal therapy exists. Treatment can become especially difficult due to progressive anaemia or when anticoagulant or anti-thrombotic therapy becomes necessary. Screening for pulmonary arteriovenous malformations (PAVM) should be performed in all confirmed and suspected patients. Treatment by percutaneous transcatheter embolotherapy and antibiotic prophylaxis is normally effective for PAVM. Cerebral or hepatic vascular malformations and rare manifestations need to be evaluated on a case-by-case basis to determine the best course of action for treatment.

Prevalence of thoracic aortopathy in patients with juvenile Polyposis Syndrome-Hereditary Hemorrhagic Telangiectasia due to SMAD4

Hereditary hemorrhagic telangiectasia (HHT) is characterized by abnormal vascular structures that may present as epistaxis, telangiectasias, and/or arteriovenous malformations. The genes associated with HHT (ACVRL1, ENG, and SMAD4) are members of the TGFβ pathway. Other syndromes associated with abnormalities in TGFβ signaling include Marfan syndrome, Loeys-Dietz syndrome and related disorders. These disorders have aortic disease as a prominent finding. While there are case reports of patients with HHT and aortopathy (dilatation/aneurysm, dissection, and rupture), this has not been systematically investigated. We conducted a retrospective chart review to determine the prevalence of aortopathy in an HHT cohort. Patients from a single institution were identified who met the Curacao Criteria for a clinical diagnosis of HHT and/or had a mutation in ACVRL1, ENG, or SMAD4 and underwent echocardiogram. Two-dimensional echocardiograms were reviewed by a single pediatric cardiologist, and data were collected on demographics, genotype, HHT features, aortic root measurements, past medical history, and family history. Z scores and nomograms were utilized to identify abnormal results. Twenty-six patients from 15 families (one ACVRL1, four ENG, eight SMAD4, and two clinical diagnoses) were included in the analysis. Aortopathy was found in 6/26 (23%) patients; all had SMAD4 mutations. In our cohort, 6/16 (38%) SMAD4 mutation carriers had evidence of aortopathy. These data suggest that aortopathy could be part of the spectrum of SMAD4-induced HHT manifestations. Routine aortic imaging, including measurements of the aorta, should be considered in patients with SMAD4 mutations to allow for appropriate medical and surgical recommendations.

A novel endoglin mutation in hereditary hemorrhagic telangiectasia type 1: a case report

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant disorder characterized by aberrant vascular development. Mutations in two genes, endoglin (ENG) and activin receptor-like kinase 1 (ACVRL1) are associated with HHT. The present case study revealed the molecular diagnosis in a family exhibiting the clinical features of HHT disease. The coding exon and flanking intronic regions of the ENG and ACVRL1 genes were sequenced and a novel mutation in exon 10 of ENG was observed in the family. The mutation (c.1426C>T) in exon 10 of the ENG gene caused a G476X mutation, which results in a premature stop codon and a truncated ENG protein. This finding demonstrated a novel mutation in the ENG gene in a Chinese family, which suggested that a truncated ENG protein may cause HHT. The present study established a genetic test to confirm the clinical diagnosis in individuals and provide an opportunity for early detection and management of the disease.

Hereditary hemorrhagic telangiectasia: genetics and molecular diagnostics in a new era

Hereditary hemorrhagic telangiectasia (HHT) is a vascular dysplasia characterized by telangiectases and arteriovenous malformations (AVMs) in particular locations described in consensus clinical diagnostic criteria published in 2000. Two genes in the transforming growth factor-beta (TGF-β) signaling pathway, ENG and ACVRL1, were discovered almost two decades ago, and mutations in these genes have been reported to cause up to 85% of HHT. In our experience, approximately 96% of individuals with HHT have a mutation in these two genes, when published (Curaçao) diagnostic criteria for HHT are strictly applied. More recently, two additional genes in the same pathway, SMAD4 and GDF2, have been identified in a much smaller number of patients with a similar or overlapping phenotype to HHT. Yet families still exist with compelling evidence of a hereditary telangiectasia disorder, but no identifiable mutation in a known gene. Recent availability of whole exome and genome testing has created new opportunities to facilitate gene discovery, identify genetic modifiers to explain clinical variability, and potentially define an increased spectrum of hereditary telangiectasia disorders. An expanded approach to molecular diagnostics for inherited telangiectasia disorders that incorporates a multi-gene next generation sequencing (NGS) HHT panel is proposed.

Clinical implications of pulmonary shunting on saline contrast echocardiography

Pulmonary right-to-left shunting can be encountered using transthoracic contrast echocardiography (TTCE) with agitated saline. Diseases associated with pulmonary shunting on saline TTCE include hereditary hemorrhagic telangiectasia (HHT), hepatopulmonary syndrome, and some congenital heart defects after partial or complete cavopulmonary anastomosis. Furthermore, small pulmonary shunts on saline TTCE are also documented in a proportion of healthy individuals. Pulmonary shunting carries the risk for severe neurologic complications due to paradoxical embolization. In HHT, additional chest computed tomography is recommended in case of any pulmonary shunt detected on saline TTCE, to evaluate the feasibility for transcatheter embolotherapy of pulmonary arteriovenous malformations. Furthermore, antibiotic prophylaxis is advised in case of any pulmonary shunt on saline TTCE to prevent brain abscesses after procedures with risk for bacteremia. The present review provides an overview of important aspects of pulmonary shunting and its detection using saline TTCE. Furthermore, advances in understanding the clinical implications of different pulmonary shunt grades on saline TTCE are described. It appears that small pulmonary shunts on saline TTCE (grade 1) lack any clinical implication, as these shunts cannot be used as a diagnostic criterion for HHT, are not associated with an increased risk for neurologic complications, and represent pulmonary arteriovenous malformations too small for subsequent endovascular treatment. This implies that additional chest computed tomography could be safely withheld in all persons with only small pulmonary shunts on saline TTCE and sets the stage for further discussion about the need for antibiotic prophylaxis in these subjects. Besides further optimization of the current screening algorithm for the detection of pulmonary arteriovenous malformations in HHT, these observations can be of additional clinical importance in other diseases associated with pulmonary shunting and in those healthy individuals with documented small pulmonary shunts on saline TTCE.

Optimal management of hereditary hemorrhagic telangiectasia

Hereditary hemorrhagic telangiectasia (HHT), also known by the eponym Osler-Weber-Rendu syndrome, is a group of related disorders inherited in an autosomal dominant fashion and characterized by the development of arteriovenous malformations (AVM) in the skin, mucous membranes, and/or internal organs such as brain, lungs, and liver. Its prevalence is currently estimated at one in 5,000 to 8,000. Most cases are due to mutations in the endoglin (HHT1) or ACVRLK1 (HHT2) genes. Telangiectasias in nasal and gastrointestinal mucosa generally present with recurrent/chronic bleeding and iron deficiency anemia. Larger AVMs occur in lungs (~40%-60% of affected individuals), liver (~40%-70%), brain (~10%), and spine (~1%). Due to the devastating and potentially fatal complications of some of these lesions (for example, strokes and brain abscesses with pulmonary AVMs), presymptomatic screening and treatment are of utmost importance. However, due to the rarity of this condition, many providers lack an appreciation for the whole gamut of its manifestations and complications, age-dependent penetrance, and marked intrafamilial variation. As a result, HHT remains frequently underdiagnosed and many families do not receive the appropriate screening and treatments. This article provides an overview of the clinical features of HHT, discusses the clinical and genetic diagnostic strategies, and presents an up-to-date review of literature and detailed considerations regarding screening for visceral AVMs, preventive modalities, and treatment options.