A disease locus for hereditary haemorrhagic telangiectasia maps to chromosome 9q33-34

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.

High risk of ischaemic stroke amongst patients with hereditary haemorrhagic telangiectasia

BACKGROUND AND PURPOSE

Hereditary haemorrhagic telangiectasia (HHT) is a genetic disease with fragile blood vessels and vascular malformations, potentially causing neurological manifestations, including stroke and cerebral abscesses. The study aimed to investigate neurological manifestations in the Danish HHT database, focusing on pulmonary arteriovenous malformations (PAVMs) as a risk factor for cerebral events.

METHODS

Retrospective analysis of the Danish HHT database was conducted, cross-referencing neurological outcomes with the Danish Apoplexy Register for accuracy. Patients were stratified by HHT type. Primary outcomes included ischaemic stroke, transient ischaemic attack and cerebral haemorrhage. Secondary outcomes comprised age, age at HHT diagnosis, age at cerebral ischaemic event, and PAVM and cerebral arteriovenous malformation status.

RESULTS

Six hundred and sixty-four HHT patients were included. PAVM was diagnosed in 54% of patients, with higher prevalence in HHT type 1 (70%) compared to HHT type 2 (34%) and juvenile polyposis HHT (66%). Ischaemic stroke or transient ischaemic attack occurred in 12.5%, with a higher risk associated with macroscopic PAVM. Logistic regression showed a nearly 10 times increased risk of ischaemic stroke with macroscopic PAVM. Cerebral abscesses occurred in 3.2% of patients, all with macroscopic PAVM. Incomplete PAVM closure increased cerebral abscess risk.

CONCLUSION

This study provides valuable insights into the prevalence of neurological manifestations and vascular events in HHT patients. The presence of PAVM was associated with an increased risk of ischaemic stroke, highlighting the importance of early screening and intervention. The findings emphasize the need for comprehensive management strategies targeting both vascular and neurological complications in HHT patients, especially regarding secondary stroke prevention.

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.

Molecular and Genetic Profiling for Precision Medicines in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a rare and chronic lung disease characterized by progressive occlusion of the small pulmonary arteries, which is associated with structural and functional alteration of the smooth muscle cells and endothelial cells within the pulmonary vasculature. Excessive vascular remodeling is, in part, responsible for high pulmonary vascular resistance and the mean pulmonary arterial pressure, increasing the transpulmonary gradient and the right ventricular “pressure overload”, which may result in right ventricular (RV) dysfunction and failure. Current technological advances in multi-omics approaches, high-throughput sequencing, and computational methods have provided valuable tools in molecular profiling and led to the identification of numerous genetic variants in PAH patients. In this review, we summarized the pathogenesis, classification, and current treatments of the PAH disease. Additionally, we outlined the latest next-generation sequencing technologies and the consequences of common genetic variants underlying PAH susceptibility and disease progression. Finally, we discuss the importance of molecular genetic testing for precision medicine in PAH and the future of genomic medicines, including gene-editing technologies and gene therapies, as emerging alternative approaches to overcome genetic disorders in PAH.

Angiopoietin-2 Inhibition Rescues Arteriovenous Malformation in a Smad4 Hereditary Hemorrhagic Telangiectasia Mouse Model

BACKGROUND

Hereditary hemorrhagic telangiectasia is an autosomal dominant vascular disorder caused by heterozygous, loss-of-function mutations in 4 transforming growth factor beta (TGFβ) pathway members, including the central transcriptional mediator of the TGFβ pathway, Smad4. Loss of Smad4 causes the formation of inappropriate, fragile connections between arteries and veins called arteriovenous malformations (AVMs), which can hemorrhage leading to stroke, aneurysm, or death. Unfortunately, the molecular mechanisms underlying AVM pathogenesis remain poorly understood, and the TGFβ downstream effectors responsible for hereditary hemorrhagic telangiectasia-associated AVM formation are currently unknown.

METHODS

To identify potential biological targets of the TGFβ pathway involved in AVM formation, we performed RNA- and chromatin immunoprecipitation-sequencing experiments on BMP9 (bone morphogenetic protein 9)-stimulated endothelial cells (ECs) and isolated ECs from a Smad4-inducible, EC-specific knockout ( Smad4-iECKO) mouse model that develops retinal AVMs. These sequencing studies identified the angiopoietin-Tek signaling pathway as a downstream target of SMAD4. We used monoclonal blocking antibodies to target a specific component in this pathway and assess its effects on AVM development.

RESULTS

Sequencing studies uncovered 212 potential biological targets involved in AVM formation, including the EC surface receptor, TEK (TEK receptor tyrosine kinase) and its antagonistic ligand, ANGPT2 (angiopoietin-2). In Smad4-iECKO mice, Angpt2 expression is robustly increased, whereas Tek levels are decreased, resulting in an overall reduction in angiopoietin-Tek signaling. We provide evidence that SMAD4 directly represses Angpt2 transcription in ECs. Inhibition of ANGPT2 function in Smad4-deficient mice, either before or after AVMs form, prevents and alleviates AVM formation and normalizes vessel diameters. These rescue effects are attributed to a reversion in EC morphological changes, such as cell size and shape that are altered in the absence of Smad4.

CONCLUSIONS

Our studies provide a novel mechanism whereby the loss of Smad4 causes increased Angpt2 transcription in ECs leading to AVM formation, increased blood vessel calibers, and changes in EC morphology in the retina. Blockade of ANGPT2 function in an in vivo Smad4 model of hereditary hemorrhagic telangiectasia alleviated these vascular phenotypes, further implicating ANGPT2 as an important TGFβ downstream mediator of AVM formation. Therefore, alternative approaches that target ANGPT2 function may have therapeutic value for the alleviation of hereditary hemorrhagic telangiectasia symptoms, such as AVMs.

Variant analysis in Chinese families with hereditary hemorrhagic telangiectasia

Background

Hereditary hemorrhagic telangiectasia (HHT) is a vascular dysplasia disorder characterized by epistaxis, mucocutaneous telangiectasias and arteriovenous malformations in internal organs. Recurrent epistaxis is the primary complaint in 90%‐96% of HHT patients and the other symptoms come with age. The aim of this study was to analyze HHT‐associated gene variant spectrum in Chinese HHT patients and to assess whether genetic testing could contribute to the early diagnosis.

Methodology/Principal

Thirty one HHT families including 62 individuals were recruited. Variants in the coding regions of four genes involved in HHT were amplified and analyzed using Sanger sequencing and multiplex ligation‐dependent probe amplification (MLPA).

Results

Twenty unique variants, including 8 novel variants were found in 24 of the 31 (77.4%) kindred. Diagnosis is confirmed for 7 possible individuals from 6 kindred. Thirteen ACVRL1 variants were detected from 17 isolated HHT families. Variants in ACVRL1 from 8/17 (47.1%) families were located in exon8. Seven ENG variants were found in 7 unrelated families throughout the coding region.

Conclusion

We conclude that ACVRL1 gene variant is 2.4 times more prevalent than that in ENG in Chinese individuals with HHT, and exon8 of the ACVRL1 gene may be a hotspot region. Genetic testing could contribute to early diagnosis for HHT.

Osler-Weber-Rendu Syndrome in Relation to Dermatology

Osler-Weber-Rendu syndrome, also known as hereditary hemorrhagic telangiectasia, is a rare autosomal dominant disorder with an estimated worldwide prevalence of 1 case per 10,000 population. Its clinical manifestations are the result of arteriovenous malformations characterized by telangiectases that can affect the skin, mucous membranes, and solid organs and cause life-threatening conditions, such as liver disease, systemic emboli, and heart failure. Timely diagnosis is thus essential in order to prevent disease-related complications and offer genetic counseling to families. We review the clinical features of Osler-Weber-Rendu syndrome with a focus on mucocutaneous manifestations and their treatment.

EphrinB2-EphB4-RASA1 Signaling in Human Cerebrovascular Development and Disease

Recent whole exome sequencing studies in humans have provided novel insight into the importance of the ephrinB2-EphB4-RASA1 signaling axis in cerebrovascular development, corroborating and extending previous work in model systems. Here, we aim to review the human cerebrovascular phenotypes associated with ephrinB2-EphB4-RASA1 mutations, including those recently discovered in Vein of Galen malformation: the most common and severe brain arteriovenous malformation in neonates. We will also discuss emerging paradigms of the molecular and cellular pathophysiology of disease-causing ephrinB2-EphB4-RASA1 mutations, including the potential role of somatic mosaicism. These observations have potential diagnostic and therapeutic implications for patients with rare congenital cerebrovascular diseases and their families.

Screening children for pulmonary arteriovenous malformations: Evaluation of 18 years of experience

BACKGROUND

Hereditary Hemorrhagic Telangiectasia (HHT) is an autosomal dominant disease with multi-systemic vascular dysplasia. Early diagnosis through screening is important to prevent serious complications. How best to screen children of affected parents for pulmonary arteriovenous malformations (PAVMs) is often subject to debate. Transthoracic contrast echocardiogram (TTCE) is considered optimal in screening for PAVMs in adults. Guidelines for the screening of children are not specific, reflecting the lack of scientific evidence on the best method to use.

OBJECTIVE

Aims of this study are (i) to evaluate our current screening method, consisting of history, physical examination, pulse oximetry, and chest radiography and (ii) to assess whether postponing more invasive screening for PAVMs until adulthood is safe.

METHODS

This is a prospective observational cohort study using a patient database.

RESULTS

Over a period of 18 years (mean follow-up 9.21 years, SD 4.72 years), 436 children from HHT families were screened consecutively. A total of 175/436 (40%) children had a diagnosis of HHT. PAVMs were detected in 39/175 (22%) children, 33/39 requiring treatment by embolotherapy. None of the screened children suffered any PAVM-associated complications with this screening method.

CONCLUSION

This study shows that a conservative screening method during childhood is sufficient to detect large PAVMs and protect children with HHT for PAVM-related complications. Postponing TTCE and subsequent chest CT scanning until adulthood to detect any smaller PAVMs does not appear to be associated with major risk.

Intravenous Bevacizumab Therapy in a Patient with Hereditary Hemorrhagic Telangiectasia, ENG E137K, Alcoholic Cirrhosis, and Portal Hypertension

Intravenous bevacizumab decreased mucosal bleeding in some patients with hereditary hemorrhagic telangiectasia (HHT). We treated a 47-year-old male who had HHT, severe epistaxis, and gastrointestinal bleeding, alcoholic cirrhosis, and portal hypertension with intravenous bevacizumab 2.5 mg/kg every 2 weeks. We tabulated these measures weekly during weeks 1–33 (no bevacizumab); 34–57 (bevacizumab); and 58–97 (no bevacizumab): hemoglobin (Hb) levels; platelet counts; units of transfused packed erythrocytes (PRBC units); and quantities of iron infused as iron dextran to support erythropoiesis. We performed univariate and multivariable analyses. We sequenced his ENG and ACVRL1 genes. Epistaxis and melena decreased markedly during bevacizumab treatment. He reported no adverse effects due to bevacizumab. Mean weekly Hb levels were significantly higher and mean weekly PRBC units and quantities of intravenous iron were significantly lower during bevacizumab treatment. We performed a multiple regression on weekly Hb levels using these independent variables: bevacizumab treatment (dichotomous); weekly platelet counts; weekly PRBC units; and weekly quantities of intravenous iron. There was 1 positive association: (bevacizumab treatment; p = 0.0046) and 1 negative association (PRBC units; p = 0.0004). This patient had the novel ENG mutation E137K (exon 4; c.409G→A). Intravenous bevacizumab treatment 2.5 mg/kg every 2 weeks for 24 weeks was well-tolerated by a patient with HHT due to ENG E137K and was associated with higher weekly Hb levels and fewer weekly PRBC units.

WITHDRAWN: The Role of capsule endoscopy and device assisted enteroscopy for small bowel lesions in hereditary hemorrhagic telangiectasia

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Life expextancy of parents with Hereditary Haemorrhagic Telangiectasia

Background

Hereditary Haemorrhagic Telangiectasia (HHT) is an autosomal dominant disease associated with epistaxis, arteriovenous malformations and telangiectasias. Disease complications may result in premature death.

Method

We investigated life-expectancies of parents of HHT patients compared with their non-HHT partners using self- or telephone-administered questionnaires sent to their children. Patients were extracted from the databases of 2 participating HHT Centres: the Toronto HHT Database (Toronto, Canada) and the St. Antonius Hospital HHT Database (Nieuwegein, The Netherlands).

Results

Two hundred twenty five/407 (55 %) of respondents were included creating HHT- (n = 225) and control groups (n = 225) of equal size. Two hundred thirteen/225 (95 %) of the HHT group had not been screened for organ involvement of the disease prior to death. The life expectancy in parents with HHT was slightly lower compared to parents without (median age at death 73.3 years in patients versus 76.6 years in controls, p0.018). Parents with ACVRL 1 mutations had normal life expectancies, whereas parents with Endoglin mutations died 7.1 years earlier than controls (p = 0.024). Women with Endoglin mutations lived a median of 9.3 years shorter than those without (p = 0.04). Seven/123 (5 %) of deaths were HHT related with a median age at death of 61.5 years (IQ range 54.4–67.7 years).

Conclusion

Our study showed that the life expectancy of largely unscreened HHT patients was lower than people without HHT. Female patients with Endoglin mutations were most strikingly at risk of premature death from complications. These results emphasize the importance of referring patients with HHT for screening of organ involvement and timely intervention to prevent complications.

Neuroradiological Manifestations of Hereditary Hemorrhagic Telangiectasia in 139 Japanese Patients

The purpose of this study is to report the neuroradiological manifestations of hereditary hemorrhagic telangiectasia (HHT). One hundred and thirty-nine Japanese HHT patients (73 men and 66 women, aged 2–78 years) were included in this study. Diagnosis of HHT was based on genetic analysis and/or clinical diagnosis of Curaçao. They included 68 HHT1 and 37 HHT2 patients. Essentially, all patients underwent brain magnetic resonance imaging (MRI) and pulmonary computed tomography (CT). Contrast enhanced studies of brain MRI and hepatic CT were performed in a subset of patients. Catheter cerebral angiography was performed when indicated. Their neuroradiological features were reviewed retrospectively. Various imaging abnormalities were found. Brain arteriovenous malformations (AVMs) were observed in 27/136 patients (19.9%, 21 patients with HHT1 and 1 patient with HHT2). Pulmonary arteriovenous fistulas (AVFs) were found in 73/137 patients (65.2%, 45 patients with HHT1 and 6 patients with HHT2). Cerebral infarction and brain abscess were found in 17 patients and 3 patients with pulmonary AVFs, respectively. T1 high lesions in the basal ganglia suggestive of porto-venous shunts were observed in 51/136 patients (37.5%, 9 patients with HHT1 and 28 patients with HHT2). Hepatic AVMs were observed in 61/136 patients (44.9%, 15 patients in HHT1 and 29 patients in HHT2). Brain AVMs and pulmonary AVFs were more common in HHT1 than in HHT2 (both p < 0.01), but hepatic AVMs were conversely more common in HHT2 than in HHT1 (p < 0.01). In conclusion, HHT patients present with a variety of neuroradiological manifestations, which are related to substantial causes of morbid-mortality in HHT.

[Gene analysis in a family of hereditary hemorrhagic telangiectasia]

OBJECTIVE

To investigate the clinical feature of a family with hereditary hemorrhagic telangiectasia (HHT), and to study the mutation of its related genes.

METHODS

Medical histories of the family were analyzed to detect HHT patients according to the diagnostic criteria. ENG and ALK-1 genes of the proband and her two daughters were analyzed. DNA from the three patients' peripheral blood was extracted. The exons 2-10 and their intron-exon boundaries of ALK1 were amplified with PCR, and then the PCR products were sequenced and analyzed to identify the mutation.

RESULTS

There were 11 people in 41 family members of 4 generations were diagnosed as HHT. The proband and her two daughters suffered from multiple organ damage, the younger daughter appeared only imaging features instead of corresponding clinical symptoms. A missense mutation at the 1321 bp of cDNA (c.1321G>A) was detected in the exon 9 of ALK1, which resulted in valine 441 to methionine replacement in ALK-1 protein (p.Val441Met).

CONCLUSION

A Chinese family with HHT was studied and a missense mutation (c.1321G>A, p.Val441Met) of ALK-1 was discovered. This mutation is the genetic basis of the family with HHT and is reported for the first time in China. This research will not only help to further investigate molecular mechanism of pathogenesis of HTT, but also provide evidences and references for the following gene screening and genetic counseling on HTT family members.

A Spinal Arteriovenous Fistula in a 3-Year Old Boy

We present a case of a 3-year-old boy with neurodegeneration. Family history reveals Rendu-Osler-Weber disease. Magnetic resonance imaging (MRI) of the spinal cord and spinal angiography showed a spinal arteriovenous fistula with venous aneurysm, causing compression of the lumbar spinal cord. Embolisation of the fistula was executed, resulting in clinical improvement. A week after discharge he was readmitted with neurologic regression. A second MRI scan revealed an intraspinal epidural haematoma and increase in size of the aneurysm with several new arterial feeders leading to it. Coiling of the aneurysm and fistulas was performed. Postoperative, the spinal oedema increased despite corticoids, causing more extensive paraplegia of the lower limbs and a deterioration of his mental state. A laminectomy was performed and the aneurysm was surgically removed. Subsequently, the boy recovered gradually. A new MRI scan after two months showed less oedema and a split, partly affected spinal chord. This case shows the importance of excluding possible arteriovenous malformations in a child presenting with progressive neurodegeneration. In particular when there is a family history for Rendu-Osler-Weber disease, scans should be performed instantly to rule out this possibility. The case also highlights the possibility of good recovery of paraplegia in paediatric Rendu-Osler-Weber patients.

Brain arteriovenous malformations in patients with hereditary hemorrhagic telangiectasia: clinical presentation and anatomical distribution

BACKGROUND

Hereditary hemorrhagic telangiectasia is an autosomal dominant genetic disease with a wide array of vascular malformations involving multiple organs. Brain arteriovenous malformations can lead to intracranial hemorrhage and are often diagnosed only after patients become symptomatic. Early diagnosis and interventional treatment may prevent neurologic sequelae or death. Because of the rarity of defined cases, the spectrum of presentations in children with brain arteriovenous malformations and hereditary hemorrhagic telangiectasia has not been explored in detail. Here, we report our experience in children with hereditary hemorrhagic telangiectasia and brain arteriovenous malformations regarding both disease manifestations at presentation and the spectrum of brain arteriovenous malformation manifestations.

METHODS

A retrospective review of demographics, clinical manifestations, and brain magnetic resonance imaging/computed tomography scan findings in 115 patients with confirmed hereditary hemorrhagic telangiectasia (HHT) was conducted using the Hospital for Sick Children's HHT Clinic database for the years 1997-2012.

RESULTS

Eleven patients (four girls and seven boys) were diagnosed with hereditary hemorrhagic telangiectasia and brain arteriovenous malformations during this period. Five patients initially presented with epistaxis, four presented with intracranial hemorrhage, and two were asymptomatic with a positive family history of confirmed hereditary hemorrhagic telangiectasia. Although all children had an index case with hereditary hemorrhagic telangiectasia in the family, in three patients, hereditary hemorrhagic telangiectasia was not diagnosed before the child's presentation with intracranial hemorrhage. Multiple brain arteriovenous malformations were found in five patients, with one patient having bithalamic arteriovenous malformations.

CONCLUSIONS

This study highlights the importance of both family history and early clinical signs to prompt further diagnostic testing to avoid intracranial hemorrhage from brain arteriovenous malformations in children with hereditary hemorrhagic telangiectasia.

BMP9 mutations cause a vascular-anomaly syndrome with phenotypic overlap with hereditary hemorrhagic telangiectasia

Hereditary hemorrhagic telangiectasia (HHT), the most common inherited vascular disorder, is caused by mutations in genes involved in the transforming growth factor beta (TGF-β) signaling pathway (ENG, ACVRL1, and SMAD4). Yet, approximately 15% of individuals with clinical features of HHT do not have mutations in these genes, suggesting that there are undiscovered mutations in other genes for HHT and possibly vascular disorders with overlapping phenotypes. The genetic etiology for 191 unrelated individuals clinically suspected to have HHT was investigated with the use of exome and Sanger sequencing; these individuals had no mutations in ENG, ACVRL1, and SMAD4. Mutations in BMP9 (also known as GDF2) were identified in three unrelated probands. These three individuals had epistaxis and dermal lesions that were described as telangiectases but whose location and appearance resembled lesions described in some individuals with RASA1-related disorders (capillary malformation-arteriovenous malformation syndrome). Analyses of the variant proteins suggested that mutations negatively affect protein processing and/or function, and a bmp9-deficient zebrafish model demonstrated that BMP9 is involved in angiogenesis. These data confirm a genetic cause of a vascular-anomaly syndrome that has phenotypic overlap with HHT.

An intron mutation in the ACVRL1 may be associated with a transcriptional regulation defect in a Chinese family with hereditary hemorrhagic telangiectasia

Purpose

To identify a novel pathogenic gene mutation present in a Chinese family with hereditary hemorrhagic telangiectasia (HHT) and to determine if an intron mutation may influence the transcriptional activity of the ACVRL1 gene.

Methods

HHT family members were ascertained following the presentation of proband and involved subjects. All family members (n = 5) and 113 healthy individuals were genotyped for the variant in intron 6 c.772+27G>C of ACVRL1 gene. The genomic structure of ACVRL1 in affected HHT patients and healthy individuals was determined by long range PCR and sequencing. The expression of ACVRL1 mRNA and protein in patients with HHT was evaluated using real-time polymerase chain reaction and immunoblot analysis. Luciferase activity assay and electrophoretic mobility shift assay (EMSA) were performed to uncover the mechanism of intron-related transcriptional regulation.

Results

Only one novel mutation in intron 6 (c.772+27G>C) of ACVRL1 gene, no other mutation, abnormal splice, gross genomic deletion or rearrangement was found in this HHT2 family. Compared with healthy individuals, ACVRL1 mRNA and protein were significantly decreased in affected HHT2 individuals. Luciferase activity assay demonstrated that the transcriptional activity of the mutated ACVRL1 was significantly lower than that of the wild-type of intron 6; EMSA results showed that intron 6 c.772+27G>C mutation was able to inhibit the binding of transcriptional factor Sp1.

Conclusions

A novel intron mutation in ACVRL1 gene is associated with familial HHT2. The mechanisms may be involved in the down-regulation of ACVRL1 gene transcription.

Brain arteriovenous malformations associated with hereditary hemorrhagic telangiectasia: gene-phenotype correlations

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant genetic disease with a wide spectrum of vascular malformations (VMs) involving multiple organs. Nine to 16% of patients with HHT harbor brain arteriovenous malformations (AVMs), which can cause intracranial hemorrhage (ICH). Our objective was to study clinical manifestations of brain AVMs in patients with HHT and correlate these with the specific gene mutated. We reviewed records of 171 patients with HHT and brain AVMs. A history of ICH was found in 27% (41/152) patients, with a mean age of 26 ± 18 range, (0-68) years. All of patients with ICH were neurologically asymptomatic prior to ICH. Multiple brain AVMs were found in 23% (170/39) of patients on initial examination. Genetic test results were available in 109 (64%) patients. Mutations in ENG, ACVRL1, and SMAD4 were present in 75 (69%), 18 (17%), and 2 (2%), respectively. A history of ICH was reported in 24% of patients with an ENG mutation and 27% of patients with an ACVRL1 mutation, with a mean age of 26 ± 16 (range, 2-50) and 18 ± 21 (0-48) years, respectively. No statistically significant differences in age at first brain AVM diagnosis, prevalence of ICH history, age at ICH, or other manifestations of brain AVMs were observed among gene groups. In conclusion, no evidence for differences in brain AVM characteristics was observed among HHT gene groups, although we cannot exclude clinically important differences. Larger studies are needed to further guide brain AVM screening decisions in patients with HHT.

Gastric angiodysplasia in a hereditary hemorrhagic telangiectasia type 2 patient

Hereditary hemorrhagic telangiectasia (HHT) is a rare autosomal-dominantly inherited disease that occurs in approximately one in 5000 to 8000 people. Clinical diagnosis of HHT is made when a person presents three of the following four criteria: family history, recurrent nosebleeds, mucocutaneous telangiectasis, and arteriovenous malformations (AVM) in the brain, lung, liver and gastrointestinal (GI) tract. Although epistaxis is the most common presenting symptom, AVMs affecting the lungs, brain and GI tract provoke a more serious outcome. Heterozygous mutations in endoglin, activin receptor-like kinase 1 (ACVRL1; ALK1), and SMAD4, the genes involved in the transforming growth factor-β family signaling cascade, cause HHT. We report here the case of a 63 year-old male patient who presented melena and GI bleeding episodes, proven to be caused by bleeding from multiple gastric angiodysplasia. Esophagogastroduodenoscopy revealed multiple angiodysplasia throughout the stomach. Endoscopic argon plasma coagulation was performed to control bleeding from a gastric angiodysplasia. The patient has been admitted several times with episodes of hemoptysis and hematochezia. One year ago, the patient was hospitalized due to right-sided weakness, which was caused by left basal ganglia hemorrhage as the part of HHT presentation. In family history, the patient’s mother and elder sister had died, due to intracranial hemorrhage, and his eldest son has been suffered from recurrent epistaxis for 20 years. A genetic study revealed a mutation in exon 3 of ALK1 (c.199C > T; p.Arg67Trp) in the proband and his eldest son presenting epistaxis.

An unusual solitary endobronchial pulmonary arteriovenous malformation in a 10 year-old child

Pulmonary arteriovenous malformations (PAVMs) are relatively rare in children. They may occur both as single isolated anomalies and, much more commonly, as one of many widely distributed arteriovenous malformations (AVMs) in other organs and anatomic locations such as the liver, brain, nose and spine. The latter phenotypically defines the condition known as Hemorrhagic Hereditary Telengiectasia (HHT). We report a case of a 10 year-old female with an isolated endobronchial right lower lobe PAVM. The patient's chest radiograph and fine-cut contrast-enhanced CT (CECT) of the neck and thorax were both uncharacteristically normal and, hence, non-diagnostic. Surgical lobectomy was the only means by which to both diagnose and treat this life-threatening condition. This unique case points out the dilemma facing the physician in such a case with only two management options neither of which is ideal: to either obtain a diagnosis with biopsy which is minimally invasive yet life-threatening due to the potential for fatal hemorrhage, or to perform a pulmonary lobectomy which entails removal of an entire lobe of the lung without a pre-operatively confirmed indication to justify the procedure. To our knowledge, this is the first reported case of a child with an endobronchial PAVM who did not carry the diagnosis of HHT, had normal chest radiography, and had a normal fine-cut CECT of the neck and thorax where such a management dilemma arose. This case points out that a high index of suspicion for PAVMs must be maintained despite normal chest radiography and CECT of the chest. In such cases, empiric lobectomy becomes the sole therapeutic and definitive diagnostic intervention. We hope that such a case published in the literature serves as a guide to physicians confronting similar circumstances as the rarity of such a constellation of variables precludes higher levels of evidence reporting such as a retrospective case series or prospective randomized controlled clinical trials.

Clinical and genetic analyses of three Korean families with hereditary hemorrhagic telangiectasia

Background

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal-dominant vascular disorder, characterized by recurrent epistaxis, mucocutaneous telangiectases, and arteriovenous malformations (AVMs) in various visceral organs. Endoglin (ENG) and activin receptor-like kinase 1 (ACVRL1; ALK1), receptors for transforming growth factor-β (TGF-β) superfamily, have been identified as the principal HHT-causing genes.

Methods

Three unrelated Korean HHT patients and their asymptomatic as well as symptomatic family members were genetically diagnosed by sequencing whole exons and their flanking regions of ENG and ACVRL1. Functionality of an aberrant translation start codon, which is created by a substitution mutation at the 5'-untranslated region (UTR) of ENG found in a HHT family, was tested by transient in vitro transfection assay. Decay of the mutant transcripts was also assessed by allele-specific expression analysis.

Results

Two ENG and one ACVRL1 mutations were identified: a known ENG mutation (c.360+1G > A; p.Gly74_Tyr120del); a novel ENG mutation (c.1-127C > T); and a novel ACVRL1 mutation (c.252_253insC; p.Val85fsX168). We further validated that the 5'-UTR ENG mutation prevents translation of ENG from the biological translation initiation site of the mutant allele, and leads to degradation of the mutant transcripts.

Conclusions

This is the first experimental demonstration that a 5'-UTR mutation can prevent translation of ENG among HHT patients, and further supports the previous notion that haploinsufficiency is the primary mechanism of HHT1. Our data also underscore the importance of including exons encoding 5' UTR for HHT mutation screening.

Hereditary hemorrhagic telangiectasia: two distinct ENG deletions in one family

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant disorder characterized by aberrant vascular development. Mutations in endoglin (ENG) or activin A receptor type II-like 1 (ACVRL1) account for around 90% of HHT patients, 10% of those are large deletions or duplications. We report here the first observation of two distinct, large ENG deletions segregating in one pedigree. An ENG exon 4-7 deletion was observed in a patient with HHT. This deletion was identified in several affected family members. However, some affected family members had an ENG exon 3 deletion instead. These deletions were detected by multiplex ligation-dependent probe amplification and confirmed by mRNA sequencing and an oligo-CGH array. Linkage analysis revealed that one individual with the exon 3 deletion inherited the same chromosome from his mother who has the exon 4-7 deletion. This finding has important clinical implications because it shows that targeted family-specific mutation analysis for exon deletions could have led to the misdiagnosis of some affected family members.

Natural history and outcome of hepatic vascular malformations in a large cohort of patients with hereditary hemorrhagic teleangiectasia

BACKGROUND

Hereditary hemorrhagic telangiectasia is a genetic disease characterized by teleangiectasias involving virtually every organ. There are limited data in the literature regarding the natural history of liver vascular malformations in hemorrhagic telangiectasia and their associated morbidity and mortality.

AIM

This prospective cohort study sought to assess the outcome of liver involvement in hereditary hemorrhagic telangiectasia patients.

METHODS

We analyzed 16 years of surveillance data from a tertiary hereditary hemorrhagic telangiectasia referral center in Italy. We considered for inclusion in this study 502 consecutive Italian patients at risk of hereditary hemorrhagic telangiectasia who presented at the hereditary hemorrhagic telangiectasia referral center and underwent a multidisciplinary screening protocol for the diagnosis of hereditary hemorrhagic telangiectasia. Of the 502 individuals assessed in the center, 154 had hepatic vascular malformations and were the subject of the study; 198 patients with hereditary hemorrhagic telangiectasia and without hepatic vascular malformations were the controls. Additionally, we report the response to treatment of patients with complicated hepatic vascular malformations.

RESULTS

The 154 patients were included and followed for a median period of 44 months (range 12-181); of these, eight (5.2%) died from VM-related complications and 39 (25.3%) experienced complications. The average incidence rates of death and complications were 1.1 and 3.6 per 100 person-years, respectively. The median overall survival and event-free survival after diagnosis were 175 and 90 months, respectively. The rate of complete response to therapy was 63%.

CONCLUSIONS

This study shows that substantial morbidity and mortality are associated with liver vascular malformations in hereditary hemorrhagic telangiectasia patients.

Large spectrum of liver vascular lesions including high prevalence of focal nodular hyperplasia in patients with hereditary haemorrhagic telangiectasia: the Belgian Registry based on 30 patients

OBJECTIVES

We report the Belgian Registry of 30 patients (19 women and 11 men) with hereditary haemorrhagic telangiectasia (HHT) and liver involvement.

RESULTS

Twenty-three patients (77%) were asymptomatic. Within the seven symptomatic patients (23%), four suffered from high output cardiac failure, two died before liver transplantation and one was transplanted. Three patients developed symptomatic biliary disease, two were transplanted and one was listed. Intrahepatic shunts and a large hepatic artery (6-14 mm, mean: 9.3 mm) were found in all patients and are characteristic of liver involvement. We observed a high prevalence (47%) of asymptomatic hepatic tumours with radiological and histological characteristics of focal nodular hyperplasia (FNH) for the majority of these tumours. The histological examination of the three explanted livers revealed the coexistence of a large spectrum of hepatic vascular lesions including intrahepatic shunts, FNH, nodular regenerative hyperplasia, sinusoidal dilatation and ischaemic cholangiopathy. All these lesions should be diagnosed early to avoid invasive procedures even if a liver biopsy was performed in six of our patients without complications. The liver biopsy led to the diagnosis of HHT in one patient and to FNH in another one.

CONCLUSION

Liver involvement in HHT is characterized by a high prevalence of FNH and a large spectrum of vascular lesions such as intrahepatic shunts, nodular regenerative hyperplasia, sinusoidal dilatation and ischaemic cholangiopathy that may coexist simultaneously in the same patient.

[Rendu-Osler-Weber syndrome: an rare cause of hypoxemia in children]

Hereditary haemorrhagic telangiectasia or Rendu-Osler-Weber syndrome is a rare genetic autosomic dominant disorder with an estimated prevalence of one in 3000-5000 individuals. This multisystemic vascular dysplasia is determined by the mutation of two main genes which are endoglin (ENG) or HHT1 and ALK1 or HHT2. These mutations induce the vascular disorders which cause recurrent epistaxis and eventually multiple telangiectasias and arteriovenous visceral malformations (AVM). We report the case of an 11-year-old boy who developed severe hypoxaemia due to multiple pulmonary arteriovenous malformations.

Hereditary haemorrhagic telangiectasia

Hereditary haemorrhagic telangiectasia (also known as Osler-Weber-Rendu syndrome) is a relatively common, under-recognized autosomal-dominant disorder that results from multisystem vascular dysplasia. It is characterized by telangiectases and arteriovenous malformations of skin, mucosa and viscera. This article summarizes the clinical manifestations and the management of this disorder and its management. This review underscores an urgent need to conduct prospective multicentre studies to develop evidence-based management guidelines for this disease.

Treatment of cutaneous and mucosal telangiectases in hereditary hemorrhagic telangiectasia: Report of three cases

INTRODUCTION

Hereditary hemorrhagic telangiectasia (HHT) or Rendu-Osler-Weber disease is an autosomal dominant disorder characterized by epistaxis, mucocutaneous telangiectases and visceral arteriovenous malformations. Cutaneous telangiectases are the most obvious sign of this disorder and are not a merely cosmetic problem owing to their risk for bleeding, which may constitute an authentic matter of concern to these patients.

METHODS

Three patients with type-II HHT disease who presented cutaneous and labial lesions were treated with an intense pulsed light (IPL) system associated with a long-pulsed Nd:YAG laser (Photoderm-Vasculight, Lumenis). Labial lesions were treated with the IPL system and cutaneous lesions were treated with the IPL system and the long-pulsed Nd:YAG laser. All treatments were accomplished on an outpatient basis, without anesthesia.

RESULTS

All three patients experienced a reduction in the frequency and severity of bleeding episodes and a great cosmetic improvement, with total lesion clearance. Side effects, such as purpura, hypopigmentation, hyperpigmentation or textural changes, were not observed. Recurrences were not detected after a maximum period of 24 months of follow-up.

CONCLUSION

The combination of an IPL system and a long-pulsed Nd:YAG laser is efficient and safe for the treatment of cutaneous and labial telangiectases in patients with HHT disease and constitutes an important tool in improving their quality of life.

Mutation analysis of "Endoglin" and "Activin receptor-like kinase" genes in German patients with hereditary hemorrhagic telangiectasia and the value of rapid genotyping using an allele-specific PCR-technique

BACKGROUND

Hereditary hemorrhagic telangiectasia (HHT), also known as Rendu-Osler-Weber syndrome, is an autosomal dominant disorder which is clinically characterised by recurrent epistaxis, mucocutaneous telangiectasia and visceral arteriovenous malformations. Genetic linkage studies identified two genes primarily related to HHT: endoglin (ENG) on chromosome 9q33-34 and activin receptor-like kinase1 (ACVRL1) on chromosome 12q13. We have screened a total of 41 unselected German patients with the suspected diagnosis of HHT. Mutation analysis for the ENG and ACVRL1 genes in all patients was performed by PCR amplification. Sequences were then compared to the HHT database http://www.hhtmutation.org sequences of the ENG mRNA (accession no. BC014271.2) and the ACVRL1 mRNA (accession no. NM000020.1).

RESULTS

We identified 15 different mutations in 18 cases by direct sequencing. Among these mutations, one novel ENG mutation could be detected which has not yet been described in the literature before. The genotype-phenotype correlation was consistent with a higher frequency of pulmonary arteriovenous malformations in patients with ENG mutations than in patients with ACVRL1 mutations in our collective.

CONCLUSION

For rapid genotyping of mutations and SNPs (single nucleotide polymorphisms) in ENG and ACVRL1, allele-specific PCR methods with sequence-specific primers (PCR-SSP) were established and their value analysed.

Correlation of severity of epistaxis with nasal telangiectasias in hereditary hemorrhagic telangiectasia (HHT) patients

BACKGROUND

Hereditary hemorrhagic telangiectasia (HHT), also known as Rendu-Osler-Weber syndrome, is an autosomal dominant disease that leads to multiregional angiodysplasia. The presence of telangiectasias in nasal mucosa leads to recurrent epistaxis that affects up to 96% of patients but with unpredictable severity. Some authors have previously explained that endonasal morphology and distribution of telangiectasias can be variable too. The purpose of this study was to evaluate any possible relationship between the severity of epistaxis and the different morphology and distribution of nasal telangiectasias in HHT patients.

METHODS

A review was performed of nasal endoscopy records of 76 consecutive HHT patients treated for epistaxis between 2003 and 2007 at our institution. An evaluation was performed of severity of epistaxis in the same patient group using a questionnaire and considering frequency, intensity, duration of nosebleeds, and need for blood transfusions. Comparison of data collected on morphology and distribution of nasal telangiectasias with data collected on severity of epistaxis was performed.

RESULTS

Morphology and distribution of nasal telangiectasias showed a statistically significant correlation with frequency and intensity of epistaxis. Presence of telangiectasias endoscopically appearing as large and prominent correlates with higher frequency of epistaxis. An increase in number of nasal subsites involved correlates with higher intensity of nosebleeds.

CONCLUSION

Our data suggest that to reduce frequency and intensity of epistaxis in HHT patients, treatments should be directed also at lesions located in the posterior part of nasal fossae and especially on telangiectasias endoscopically appearing as large and prominent.

Rupture of hepatic aneurysm complicating hereditary hemorrhagic telangiectasia (Osler-Weber-Rendu disease) for which hepatic arterial coil embolization was effective

A 74-year-old woman was transferred to our hospital for further examinations because of abdominal fullness and abnormal levels of serum liver/biliary enzyme persisting for 3 weeks. She had anemia and dilatation of many capillary vessels in her fingers, palms, and tongue in addition to reporting frequent incidences of nasal bleeding in herself and her family. Abdominal ultrasonography detected a cystic lesion in the right hepatic lobe, connected to a dilated tortuous hepatic artery. A low-echoic hepatic phyma was also detected in the back of the cystic lesion. Abdominal computed tomography and magnetic resonance imaging indicated that the cystic lesion was an aneurysm and the low-echoic phyma was a hematoma. Hepatic arteriography confirmed a hepatic aneurysm, tortuous dilatation of the hepatic artery, and the complication of an arteriovenous shunt in the liver. Taking all of these findings into consideration, this case was diagnosed as hereditary hemorrhagic telangiectasia (HTT) complicated by a hepatic aneurysm causing intrahepatic hematoma. To prevent re-rupture of the aneurysm, we performed a hepatic arterial coil embolization. After therapy, no blood flow to the aneurysm was detected by ultrasonic color Doppler method and the hematoma gradually diminished. There have been no reports of a case in which hepatic arterial embolization was effective for HHT-associated hepatic aneurysm causing intrahepatic hematoma. This very rare case provides important clinical information regarding abdominal vascular complications of HTT and a less invasive treatment for them.

A fourth locus for hereditary hemorrhagic telangiectasia maps to chromosome 7

Hereditary hemorrhagic telangiectasia (HHT) is a genetically and clinically heterogeneous multisystem vascular dysplasia. Mutations of the endoglin and ACVRL1 genes are known to cause HHT. However, existence of HHT families in which linkage to these genes has been excluded has suggested that other gene(s) can cause HHT in some families. Recently, a family was reported to be linked to chromosome 5q, the HHT3 locus. Here we report on linkage results on a family with classic features of HHT, albeit a less severe phenotype with regards to epistaxis and telangiectases, in which linkage to HHT1, HHT2, and HHT3 is ruled out. Whole genome linkage analysis and fine mapping results suggested a 7 Mb region on the short arm of chromosome 7 (7p14) between STR markers D7S2252 and D7S510. We obtained a maximum two point LOD score of 3.60 with the STR marker D7S817. This region was further confirmed by haplotype analysis. These findings suggest the presence of another gene causing HHT (HHT4). The features in this family that strongly suggest the presence of a hereditary, multisystem vascular dysplasia would be easily missed during the typical evaluation and management of a patient with an AVM. This family helps emphasize the need to obtain a very detailed, targeted medical and family history for even mild, infrequent but recurring nosebleed, subtle telangiectases. Further studies of the candidate region and the identification of the gene responsible for the vascular anomalies in this family will add to our understanding of vascular morphogenesis and related disorders.

Hereditary hemorrhagic telangiectasia: an update on clinical manifestations and diagnostic measures

Hereditary hemorrhagic telangiectasia (HHT), also known as Rendu-Osler-Weber disease, is an autosomal dominant disorder of the fibrovascular tissue. It is characterized by the classic triad of (muco-)cutaneous telangiectases, arteriovenous malformations with recurrent epistaxis and hemorrhages, and inheritance. A wide variety of clinical manifestations in HHT have been described. In more than 90% of the patients, nosebleeds are the first predominant symptom, therefore ENT physicians often play a key role as far as diagnosis and management of the disease are concerned. In spite of recent diagnostic and therapeutic progress, a cure for this often burdening and handicapping disease is still not available. Apart from affecting the nose, arteriovenous malformations (AVMs) may also affect the skin, lungs, brain, liver and gastrointestinal tract. The two known genes that are implicated in HHT are endoglin (ENG) located on chromosome 9q33-q34 and activin-receptor-like kinase (ALK1) located on chromosome 12q13. Mutations of ENG are observed in HHT type 1 with an incidence up to 40% for pulmonary AVMs, whereas mutations of ALK1 are observed in HHT type 2 with an incidence of only 14% for pulmonary AVMs, which clinically distinguishes these two types of mutation. The emphasis of this paper is mainly on the clinical manifestation, molecular genetics and diagnosis of HHT, taking account of current literature on HHT in order to better understand the complexity of the disease. Recent therapeutic options in the treatment of HHT have been omitted from this paper as they are subject of a following paper. HHT is more common than previously thought and shows a broad range of different clinical organ manifestations that can be sources of substantial morbidity and mortality, making HHT a continuing challenge for many sub-specialties where interdisciplinary diagnostic screening is mandatory in the management of the disease.

Hereditary hemorrhagic telangiectasia, a vascular dysplasia affecting the TGF-beta signaling pathway

Hereditary hemorrhagic telangiectasia (HHT) is caused by mutations in endoglin (ENG; HHT1) or ACVRL1/ALK1 (HHT2) genes and is an autosomal dominant vascular dysplasia. Clinically, HHT is characterized by epistaxis, telangiectases and arteriovenous malformations in some internal organs such as the lung, brain or liver. Endoglin and ALK1 proteins are specific endothelial receptors of the transforming growth factor (TGF)-beta superfamily that are essential for vascular integrity. Genetic studies in mice and humans have revealed the pivotal role of TGF-beta signaling during angiogenesis. Through binding to the TGF-beta type II receptor, TGF-beta can activate two distinct type I receptors (ALK1 and ALK5) in endothelial cells, each one leading to opposite effects on endothelial cell proliferation and migration. The recent isolation and characterization of circulating endothelial cells from HHT patients has revealed a decreased endoglin expression, impaired ALK1- and ALK5-dependent TGF-beta signaling, disorganized cytoskeleton and the failure to form cord-like structures which may lead to the fragility of small vessels with bleeding characteristic of HHT vascular dysplasia or to disrupted and abnormal angiogenesis after injuries and may explain the clinical symptoms associated with this disease.

Mutations in endoglin and in activin receptor-like kinase 1 among Danish patients with hereditary haemorrhagic telangiectasia

Hereditary haemorrhagic telangiectasia (HHT) is a rare disorder with one per 6000-10,000 affected individuals in the general Caucasian population. HHT is genetically heterogeneous, involving at least two loci HHT1 mapping to chromosome 9q34.1 and HHT2 mapping to chromosome 12q31. The loci have been identified as endoglin (ENG) and activin receptor-like kinase 1 (ALK1). In order to gain knowledge of the genotype distribution and prevalence in the Danish population and to establish a reproducible and sensitive molecular genetic test method, we developed a denaturating gradient gel electrophoresis protocol for mutation scanning of the two loci. Twenty-five Danish HHT families were tested. A total of eight new as well as seven previously reported mutations were identified. A founder mutation was characterized present in seven families and possibly introduced around 350 years ago. In one individual, a presumed spontaneous mutation was characterized. The method developed proved to be very sensitive for mutation detection in both ENG and ALK1. Genetic screening in HHT families facilitates an early treatment strategy for silent HHT manifestations in first degree relatives.

Hereditary hemorrhagic telangiectasia is caused by the Q490X mutation of the ACVRL1 gene in a large Arab family: support of homozygous lethality

In a large Saudi Arabian family with hereditary hemorrhagic telangiectasia (HHT), we identified ACVRL1 (ALK1) nonsense mutation Q490X in 40 HHT patients and three healthy children, but neither in 11 individuals with epistaxis, 41 other healthy family members, nor in 50 healthy unrelated Saudi Arabian controls. Sequence analysis of the entire coding region of the ACVRL1 and ENG genes in five of the 11 epistaxic individuals did not reveal any other disease-causing mutation. Epistaxis seems to be a relatively common phenocopy of HHT in the family under study. One couple, both affected by HHT and carriers of Q490X, had 12 pregnancies. Three of them ended in spontaneous abortion, four in early neonatal death, and only five yielded living offspring, all of which had HHT and were Q490X heterozygous. This observation corroborates previous claims that homozygosity for HHT-causing mutations is lethal.

Cost comparison of genetic and clinical screening in families with hereditary hemorrhagic telangiectasia

Endoglin (ENG) and ALK-1 mutations cause hereditary hemorrhagic telangiecstasia (HHT), an autosomal dominant disorder leading to vascular dysplasia in the form of mucocutaneous telangiectasia and visceral arteriovenous malformations (AVMs). We proposed to compare two alternative strategies for management of HHT: screening HHT families with molecular diagnostic tests followed by targeted clinical screening versus conventional clinical screening. A decision analytic model was constructed to compare screening strategies for a hypothetical HHT family. The family consists of 1 index case and 13 relatives. The clinical screening protocol in use at the Canadian HHT Center in Toronto was assumed to be the standard of care. Unit costs for clinical screening (in Canadian dollars) were obtained from the 2003 Ontario Health Insurance Schedule of Benefits. Genetic screening costs were estimated for quantitative multiplex PCR and sequencing of Endoglin (ENG) and ALK-1 genes, as performed at HHT Solutions, Toronto. The genetic screening strategy resulted in a net cost of $4,060 per individual versus $5,975 for the clinical screening strategy. The genetic screening strategy would save $1,915 per family member or $26,810 saved per family. Sensitivity analyses revealed that the genetic screening strategy was cost saving over all plausible ranges of input variables for all hypothetical families tested. We concluded that a genetic screening strategy with targeted clinical screening is more economically attractive than conventional clinical screening and results in a reduction in the number of clinical tests for family members who do not have HHT.

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

Hereditary haemorrhagic telangiectasia (HHT) is an autosomal dominant disorder characterised by epistaxis, telangiectases, and multiorgan vascular dysplasia. The two major types of disease, HHT1 and HHT2, are caused by mutations in the ENG (endoglin) and ACVRL1 genes, respectively. The corresponding endoglin and ALK-1 proteins are specific endothelial receptors of the transforming growth factor beta superfamily essential for maintaining vascular integrity. Many mutations have been identified in ENG and ACVRL1 genes and support the haploinsufficiency model for HHT. Two more genes have recently been implicated in HHT: MADH4 mutated in a combined syndrome of juvenile polyposis and HHT (JPHT), and an unidentified HHT3 gene linked to chromosome 5. Current knowledge on the genetics of HHT is summarised, including the pathways that link the genes responsible for HHT and the potential mechanisms underlying the pathogenesis of the disease.

Hereditary hemorrhagic telangiectasia: an overview of diagnosis and management in the molecular era for clinicians

Hereditary hemorrhagic telangiectasia (Osler-Weber-Rendu syndrome) is a relatively common, underdiagnosed autosomal-dominant disorder of arteriovenous malformations and telangiectases. DNA testing for hereditary hemorrhagic telangiectasia has recently become available in North America, making presymptomatic screening available to relatives with a positive molecular diagnosis. This now enables practitioners to prevent catastrophic complications of undiagnosed pulmonary and CNS arteriovenous malformations and eliminates the need to radiographically screen all at-risk relatives shown to be unaffected by molecular testing. We review the clinical aspects of hereditary hemorrhagic telangiectasia, describe the indications, benefits, and limitations of molecular diagnostic testing for hereditary hemorrhagic telangiectasia, and provide a molecular genetics summary to facilitate genetic counseling before and after DNA testing for this complex disorder.