Genetic heterogeneity in hereditary haemorrhagic telangiectasia: possible correlation with clinical phenotype

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.

The Role and Therapeutic Implications of Inflammation in the Pathogenesis of Brain Arteriovenous Malformations

Brain arteriovenous malformations (bAVMs) are focal vascular lesions composed of abnormal vascular channels without an intervening capillary network. As a result, high-pressure arterial blood shunts directly into the venous outflow system. These high-flow, low-resistance shunts are composed of dilated, tortuous, and fragile vessels, which are prone to rupture. BAVMs are a leading cause of hemorrhagic stroke in children and young adults. Current treatments for bAVMs are limited to surgery, embolization, and radiosurgery, although even these options are not viable for ~20% of AVM patients due to excessive risk. Critically, inflammation has been suggested to contribute to lesion progression. Here we summarize the current literature discussing the role of the immune system in bAVM pathogenesis and lesion progression, as well as the potential for targeting inflammation to prevent bAVM rupture and intracranial hemorrhage. We conclude by proposing that a dysfunctional endothelium, which harbors the somatic mutations that have been shown to give rise to sporadic bAVMs, may drive disease development and progression by altering the immune status of the brain.

Epidemiology and Trends of Hereditary Hemorrhagic Telangiectasia in the United States

Background

To our knowledge, no national studies have investigated the epidemiology of hereditary hemorrhagic telangiectasia (HHT) in the United States since the incorporation of the International Statistical Classification of Diseases and Related Health Problems, 10th Revision, Clinical Modification (ICD-10 CM).

Objective

Our objective is to analyze the epidemiology of HHT from 2013 to 2017 and to determine the relationships between epistaxis and other associated complications of this rare disease.

Methods

We analyzed the epidemiology of HHT between 2013 and 2017 by accessing data of 87 709 738 patients from the Clinformatics Data Mart using ICD-9 CM and ICD-10 CM codes. Variables analyzed included age, gender, region, clinical setting of diagnosis, hospitalizations, and complications. Bivariate analyses using generalized linear models were conducted to determine the likelihood of HHT patients with epistaxis enduring associated life-threatening complications such as cerebral hemorrhage, thrombosis, and pulmonary hemorrhage compared to HHT patients without epistaxis during the study period.

Results

The prevalence of HHT increased from 6.1 to 12.1 per 100 000 persons, with patients of ages 18 to 29 years and those older than 60 years seeing the greatest percent increase. The prevalence of HHT in the Southern United States saw a 147% increase. Compared to HHT patients without epistaxis, HHT patients with epistaxis were 3.4 times more likely to experience pulmonary hemorrhage, 3.3 times more likely to have pulmonary emboli, 2.8 times more likely to experience cerebral hemorrhage, and 2.0 times more likely to have thrombosis during the study period.

Conclusion

Our national study has provided the first incidence and prevalence rates of HHT in the United States since the incorporation of the ICD-10 CM. HHT patients with epistaxis require prompt multidisciplinary treatment of their condition due to their increased risk of life-threatening complications.

Non-invasive CT screening for pulmonary arteriovenous malformations in children with confirmed hereditary hemorrhagic telangiectasia: Results from two pediatric centers

BACKGROUND

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant genetic disorder that is caused by mutations in mainly two genes, that is ENG, encoding endoglin (HHT1), or ACVRL1, encoding activin receptor-like kinase 1 (ALK-1/HHT2). HHT is characterized by recurrent epistaxis, mucocutaneous telangiectasia, and vascular visceral dysplasia responsible for visceral arteriovenous malformations (AVM).

AIM

to report the experience of two university hospitals (Trousseau, Paris, and CHIC, Creteil) with screening children for HHT and pulmonary AVM (PAVM) using high resolution computed tomography (HRCT).

METHODS

parents with confirmed HHT were offered to have their children screened for the mutation identified in their family, and informed consent was obtained. Children carrying the same mutation as their parents underwent HRCT of the chest without contrast.

RESULTS

between 2008 and 2015, 99 children were screened for HHT mutations. Mutations were identified in 59 patients, that is 24 HHT1 and 35 HHT2. Radiologic and clinical screening was possible in 52 patients (21 HHT-1 and 31 HHT-2). Among those, PAVM was identified in 13 patients (25%; n = 8 HHT1; n = 5 HHT2), and four of them required embolization therapy.

CONCLUSION

This study highlights the usefulness of genetic screening in children with known HHT family. It also suggests that a non-invasive protocol such as HRTC is an efficient approach to detect non-symptomatic lesions that are present early on in children carrying the ENG (HHT1), but also the ACVRL1 mutations (HHT2). Pediatr Pulmonol. 2017;52:642-649. © 2017 Wiley Periodicals, Inc.

Functional and splicing defect analysis of 23 ACVRL1 mutations in a cohort of patients affected by Hereditary Hemorrhagic Telangiectasia

Hereditary Hemorrhagic Telangiectasia syndrome (HHT) or Rendu-Osler-Weber (ROW) syndrome is an autosomal dominant vascular disorder. Two most common forms of HHT, HHT1 and HHT2, have been linked to mutations in the endoglin (ENG) and activin receptor-like kinase 1 (ACVRL1or ALK1) genes respectively. This work was designed to examine the pathogenicity of 23 nucleotide variations in ACVRL1 gene detected in more than 400 patients. Among them, 14 missense mutations and one intronic variant were novels, and 8 missense mutations were previously identified with questionable implication in HHT2. The functionality of missense mutations was analyzed in response to BMP9 (specific ligand of ALK1), the maturation of the protein products and their localization were analyzed by western blot and fluorescence microscopy. The splicing impairment of the intronic and of two missense mutations was examined by minigene assay. Functional analysis showed that 18 out of 22 missense mutations were defective. Splicing analysis revealed that one missense mutation (c.733A>G, p.Ile245Val) affects the splicing of the harboring exon 6. Similarly, the intronic mutation outside the consensus splicing sites (c.1048+5G>A in intron 7) was seen pathogenic by splicing study. Both mutations induce a frame shift creating a premature stop codon likely resulting in mRNA degradation by NMD surveillance mechanism. Our results confirm the haploinsufficiency model proposed for HHT2. The affected allele of ACVRL1 induces mRNA degradation or the synthesis of a protein lacking the receptor activity. Furthermore, our data demonstrate that functional and splicing analyses together, represent two robust diagnostic tools to be used by geneticists confronted with novel or conflicted ACVRL1 mutations.

Hereditary hemorrhagic telangiectasia

Background:

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant disorder, which affects various internal organs and has a tendency for bleeding. It has a classic triad of mucocutaneous telangiectasias, recurrent hemorrhages and positive familial history of first-degree relative. Epistaxis or gastrointestinal telangiectasia can be fatal in a small number of cases.

Case Report:

A 44-year-old woman came with complaints of recurrent episodes of hematemesis and epistaxis. Patient had a family history of similar complaints. Patient underwent esophagogastroduodenoscopy (EGD), which revealed telangiectasia in the stomach. Imaging of the abdomen showed features suggestive of arteriovenous shunting.

Conclusion:

HHT can remain undiagnosed for a long time, and is rarely being reported in the literature with management needing a multidisciplinary approach with early inputs from a gastroenterologist.

Soluble endoglin antagonizes Met signaling in spindle carcinoma cells

Increased levels of soluble endoglin (Sol-Eng) correlate with poor outcome in human cancer. We have previously shown that shedding of membrane endoglin, and concomitant release of Sol-Eng is a late event in chemical mouse skin carcinogenesis associated with the development of undifferentiated spindle cell carcinomas (SpCCs). In this report, we show that mouse skin SpCCs exhibit a high expression of hepatocyte growth factor (HGF) and an elevated ratio of its active tyrosine kinase receptor Met versus total Met levels. We have evaluated the effect of Sol-Eng in spindle carcinoma cells by transfection of a cDNA encoding most of the endoglin ectodomain or by using purified recombinant Sol-Eng. We found that Sol-Eng inhibited both mitogen-activated protein kinase (MAPK) activity and cell growth in vitro and in vivo. Sol-Eng also blocked MAPK activation by transforming growth factor-β1 (TGF-β1) and impaired both basal and HGF-induced activation of Met and downstream MAPK. Moreover, Sol-Eng strongly reduced basal and HGF-stimulated spindle cell migration and invasion. Both Sol-Eng and full-length endoglin were shown to interact with Met by coimmunoprecipitation experiments. However, full-length endoglin expressed at the plasma membrane of spindle carcinoma cells had no effect on Met signaling activity, and was unable to inhibit HGF-induced cell migration/invasion. These results point to a paradoxical suppressor role for Sol-Eng in carcinogenesis.

Review: the enigmatic role of endoglin in the placenta

The cellular expression, structure and function of endoglin, and its implication in several vascular disorders remain enigmatic, even 30 years after its discovery. Endoglin (CD105) is a homodimeric glycoprotein (180 kDa) constitutively expressed in the vascular endothelium. It is essential for cardiovascular development and mutations in the ENG gene lead to Hereditary Hemorrhagic Telangiectasia, a disorder characterized by arteriovenous malformations. Endoglin is also expressed in the syncytiotrophoblast throughout pregnancy, but transiently upregulated in the extravillous trophoblast of anchoring villi. Endoglin modulates responses to several TGF-β superfamily ligands and is essential for the negative regulation by TGF-β isoforms 1 and 3 of extravillous trophoblast differentiation. Membrane endoglin binds endothelial NO synthase and regulates its activation and vasomotor tone. There is also a circulating soluble form of endoglin (sEng; 65 kDa); its levels in the serum of women with preeclampsia are increased and correlated with disease severity. The exact sequence of sEng is still unresolved and the proposed mechanism of release from the syncytium by metalloproteases would not yield the expected size protein. The nature of the ligand sequestered by sEng is also an enigma. sEng is said to block the effects of TGF-β on NO-mediated vasorelaxation. However, sEng alone cannot scavenge these ligands for which it has very low affinity. sEng binds with high affinity to BMP9, which stimulates secretion from endothelial cells of the vascoconstrictor endothelin-1, also implicated in endothelial cell stabilization. It remains to be determined if scavenging of circulating BMP9 by sEng is important in preeclampsia and regulation of hypertension.

Normal and abnormal pulmonary arteriovenous shunting: occurrence and mechanisms

Severe cyanosis due to pulmonary arteriovenous fistulas occurs often after a bidirectional superior cavopulmonary anastomosis (Glenn operation) and also in some congenital anomalies in which hepatic venous blood bypasses the lungs in the first passage. Relocation of hepatic flow into the lungs usually causes these fistulas to disappear. Similar pulmonary arteriovenous fistulas are observed in hereditary haemorrhagic telangiectasia, and in liver disease (hepatopulmonary syndrome). There is no convincing identification yet of a responsible hepatic factor that produces these lesions. Candidates for such a factor are reviewed, and the possibility of angiotensin or bradykinin contributing to the fistulas is discussed.

The ALK-1/Smad1 pathway in cardiovascular physiopathology. A new target for therapy?

Activin receptor-like kinase-1 or ALK-1 is a type I cell surface receptor for the transforming growth factor-β (TGF-β) family of proteins. The role of ALK-1 in endothelial cells biology and in angiogenesis has been thoroughly studied by many authors. However, it has been recently suggested a possible role of ALK-1 in cardiovascular homeostasis. ALK-1 is not only expressed in endothelial cells but also in smooth muscle cells, myofibroblast, hepatic stellate cells, chondrocytes, monocytes, myoblasts, macrophages or fibroblasts, but its role in these cells have not been deeply analyzed. Due to the function of ALK-1 in these cells, this receptor plays a role in several cardiovascular diseases. Animals with ALK-1 haploinsufficiency and patients with mutations in Acvrl1 (the gene that codifies for ALK-1) develop type-2 Hereditary Hemorrhagic Telangiectasia. Moreover, ALK-1 heterozygous mice develop pulmonary hypertension. Higher levels of ALK-1 have been observed in atherosclerotic plaques, suggesting a possible protector role of this receptor. ALK-1 deficiency is also related to the development of arteriovenous malformations (AVMs). Besides, due to the ability of ALK-1 to regulate cell proliferation and migration, and to modulate extracellular matrix (ECM) protein expression in several cell types, ALK-1 has been now demonstrated to play an important role in cardiovascular remodeling. In this review, we would like to offer a complete vision of the role of ALK-1 in many process related to cardiovascular homeostasis, and the involvement of this protein in the development of cardiovascular diseases, suggesting the possibility of using the ALK-1/smad-1 pathway as a powerful therapeutic target.

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.

CT Manifestations of Osler-Weber-Rendu Syndrome in Liver: Report of Three Cases

Osler-Weber-Rendu syndrome is characterized by widespread telangiectasias. Its clinical manifestations depend on position and scope of the abnormal vessels. The clinical and CT data of 3 patients with Osler-Weber-Rendu syndrome were retrospectively analyzed. CT features reviewed include the change of volume and configuration of liver, presence of tortuous and irregular vessels, opacified vessel mass, arteriovenous shunt, and splenomegaly. CT is helpful for diagnosis, treatment, and follow-up of Osler-Weber-Rendu syndrome.

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.

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.

[Analysis of molecular background of hereditary haemorrhagic telangiectasia--Rendu-Osler-Weber disease--preliminary results]

INTRODUCTION

Hereditary haemorrhagic telangiectasia (HHT) known also as Rendu-Osler-Weber syndrome is an autosomal dominant disorder characterized by localized angiodysplasia due to mutations in ENG (endoglin, 9q34.1) or ALK-1 gene (the activin receptor-like kinase 1, 12q13). ENG and ALK-1 are found associated with two disease subtypes designated as HHT1 and HHT2, respectively. Subtype HHT1 remains in the frame of interest of laryngology because of frequent bleeding in head and neck region.

MATERIAL AND METHOD

The study was designed to identify a genetic background in a large family (29 individuals) with diagnosed HHT. Pedigree analysis showed autosomal dominant pattern of inheritance. Study design comprised segregation analysis to determine locus with subsequent direct sequencing of the gene. Four microsatelite markers (d9s61, d9s65, d12s368, d12s347) with high frequency of heterozygosity in population study were used.

RESULTS

The results concerning heterozygosity ranged from 15% to 53%. The established differences were not sufficient enough to indicate co-segregation of the studied loci. DNA sequence analysis in exon 11 of ENG gene did not reveal mutations. The latter result could be explained by an occurrence of mutations in other exons of ENG.

CONCLUSIONS

The study requires continuation for gene identification and precise genotype-phenotype correlation aiming for an improvement of HHT1 therapy.

Pulmonary vascular manifestations of hereditary hemorrhagic telangiectasia (rendu-osler disease)

Hereditary hemorrhagic telangiectasia (HHT) or Rendu-Osler-Weber disease is a genetic disorder with autosomal dominance and variable penetrance, characterized by epistaxis, telangiectasia and visceral manifestations of the disease. The estimated minimal prevalence is 1/10,000 inhabitants. The diagnosis is established on clinical criteria, and may be further confirmed by the identification of causative mutations in either the ENG or the ACVRL1 gene coding for endoglin and ALK1, respectively. Pulmonary vascular manifestations of HHT include pulmonary arteriovenous malformations (PAVMs; especially in patients with ENG mutations) and less frequently pulmonary hypertension (especially in patients with ACVRL1 mutations). In 15-33% of patients with HHT, PAVMs consist of abnormal communications between pulmonary arteries and pulmonary veins, causing right-to-left shunting, and thus, frequently hypoxemia and dyspnea on exertion, although PAVMs may remain asymptomatic and frequently undiagnosed unless complications occur. PAVMs result in severe and frequent complications often at a young age, which may reveal the diagnosis, e.g. transient ischemic attack and cerebral stroke (10-19% of patients), systemic severe infections and abscesses (including cerebral abscess in 5-19% of patients), and rarely massive hemoptysis or hemothorax. Infections in HHT are related to the right-to-left shunting that bypasses the pulmonary capillaries and facilitates the passage of septic or aseptic emboli into the systemic and especially cerebral circulation, and potentially to minor defects in innate immunity. Treatment of PAVMs based on transcatheter coil vaso-occlusion of the feeding artery significantly decreases right-to-left shunting, hypoxemia and dyspnea on exertion, and reduces the risk of systemic complications. Long-term follow-up is warranted after transcatheter vaso-occlusion of PAVMs due to frequent recanalization of treated PAVMs and development or growth of untreated PAVMs. Patients with HHT should be informed of the risk of PAVM and potentially severe complications occurring in heretofore asymptomatic subjects. All adult patients with HHT should be proposed systematic screening for PAVM, by contrast echocardiography (preceded by anteroposterior chest radiograph) or computed tomography of the chest. Pulmonary hypertension is rare in HHT, and may be due either to systemic arteriovenous shunting in the liver increasing cardiac output or be clinically and histologically indistinguishable from idiopathic pulmonary arterial hypertension. Pulmonary hypertension is detected by systematic examination of right cardiac cavities and tricuspid regurgitation flow at echocardiography, and the diagnosis is established by right heart catheterization.

Three novel mutations in the activin receptor-like kinase 1 (ALK-1) gene in hereditary hemorrhagic telangiectasia type 2 in Brazilian patients

Hereditary hemorrhagic telangiectasia (HHT) or Osler-Rendu-Weber disease is a systemic fibrovascular dysplasia with an autosomal dominant inheritance pattern. Mutations in two genes, endoglin and ALK-1, are known to cause HHT, both of which mediate signaling by transforming growth factor beta ligands in vascular endothelial cells. Ten patients were analyzed. Diagnosis of HHT was carried out by means of family history, recurrent bleeding, and the presence of multiple telangiectases lesions. Conformation-sensitive gel electrophoresis analyses with consistent abnormal migration patterns were cloned and sequenced using the MegaBace 1000 DNA automated analyzer. Three novel mutations were identified in the coding sequence of the ALK-1 gene in five patients and their families, which demonstrated clinical manifestations of HHT type 2. These mutations included a G insertion and a T deletion of single base pairs in exons 3 and 7, as well as missense mutations in exons 7 and 8 of the ALK-1 gene. These data indicate that loss-of-function mutations in a single allele of the ALK1 locus are sufficient to contribute to defects in maintaining endothelial integrity. We suggest the high rate of mutation detection and the small size of the ALK-1 gene make genomic sequencing a viable diagnostic test for HHT2.

Pulmonary arteriovenous malformations in hereditary hemorrhagic telangiectasia: a series of 126 patients

Hereditary hemorrhagic telangiectasia (HHT) is a genetic disorder characterized by epistaxis, telangiectasia, and visceral vascular manifestations. Infectious and ischemic central nervous system (CNS) manifestations due to embolism through pulmonary arteriovenous malformations (PAVMs) represent the main causes of morbidity. To improve the phenotypic characterization of HHT with PAVM, we conducted a retrospective multicenter study of patients with HHT and at least 1 PAVM detected by chest computed tomography (CT) and/or pulmonary angiography, with particular attention to CNS and infectious manifestations. The study included 126 patients (47 men, 79 women), with a mean age of 43.1 +/- 17.4 years; 45 patients had a mutation of the ENG gene and 16 had a mutation of ACVRL1. PAVMs were diagnosed as a result of systematic screening procedures (29%), incidental imaging findings (15%), dyspnea (22%), or CNS symptoms (13%). The PAVMs were diagnosed at a mean age of 43 +/- 17 years, with a linear distribution of diagnosis between 20 and 75 years. Dyspnea on exertion was present in 56% of patients. Four patients had a hemothorax, including 1 during pregnancy. Fifty-three CNS events directly related to HHT (excluding migraine) were observed in 35% of patients: cerebral abscess (19.0%), ischemic cerebral stroke (9.5%), transient cerebral ischemic attack (6.3%), and cerebral hemorrhage (2.4%). The median age of onset was 33 years for cerebral abscesses (range, 11-66 yr), and 53.5 years for ischemic cerebral events (range, 2-72 yr). Migraine was reported in 16% of patients. The diagnoses of PAVM and HHT were made at the time of the cerebral abscess in 13 cases (54%). Forty-three percent of patients were hypoxemic at rest. Contrast echocardiography showed intrapulmonary right-to-left shunting in 87% of tested patients. PAVMs were seen on chest radiograph in 54% of patients, and on the CT scan in all patients. One hundred five patients (83%) underwent treatment of the PAVM, by percutaneous embolization (71%) and/or by surgical resection (23%). A high frequency of CNS and infectious complications was observed in this large series of patients with HHT-related PAVM. Physicians may not be sufficiently aware of the clinical manifestations of this orphan disorder. Patients diagnosed with HHT should be informed by physicians and patient associations of the risk of PAVM-related complications, and systematic screening for PAVM should be proposed, regardless of a patient's symptoms, familial history, or genetic considerations.

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.

Clinical symptoms according to genotype amongst patients with hereditary haemorrhagic telangiectasia

BACKGROUND

Hereditary haemorrhagic telangiectasia (HHT) is a dominantly inherited disease, characterized by a wide variety of clinical manifestations, including epistaxis, gastrointestinal (GI) bleeding, pulmonary arteriovenous malformations (PAVMs) and neurological symptoms. HHT is a genetically heterogeneous disorder involving at least two loci; HHT 1 mapping to chromosome 9 q 34.1 (ENG) and HHT 2 mapping to chromosome 12 q 31 (ALK-1).

OBJECTIVE

To evaluate and describe the diversity of clinical manifestations in a Danish population of HHT patients with known HHT 1 or HHT 2 subtype.

DESIGN

Prospective clinical examination with genetic evaluation and follow-up.

SETTING

Investigation centre was Odense University Hospital. All HHT patients in the County of Fyn were included.

METHODS

HHT family members were invited to a clinical examination including registration of HHT manifestations, screening for PAVM and neurological evaluation. Blood tests were performed for analysis of disease-causing mutation, and clinical manifestations in the HHT subtypes were compared. The survival of the patients was studied in the follow-up period.

RESULTS

Included in the study were 73 HHT patients representing 18 families. In 14 of the families we identified a disease-causing mutation. Thirty-nine patients (from 10 families) had HHT1 and 16 HHT patients from four families had HHT2.

CONCLUSION

Amongst patients with HHT1 genotype the prevalence of PAVM was higher than amongst HHT patients with HHT2 genotype. HHT1 patients had experienced more severe GI bleeding than HHT2 patients. There was no significant difference in severity of epistaxis or age at debut. Finally the mortality over a 90-month observation period was not significantly increased.

Genetics of cerebrovascular disorders

Physicians must be able to recognize stroke caused by a mendelian or mitochondrial disorder. Some genetic disorders such as sickle cell anemia and Fabry disease have proven disease-specific treatments, whereas others have no effective treatment, including cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) and mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS). Proper diagnosis of a genetic disorder has prognostic value and prevents patient exposure to unnecessary and potentially harmful therapeutic agents and diagnostic tests. This article reviews the clinical and genetic features of some mendellan and mitochondrial disorders associated with ischemic stroke, hemorrhagic stroke, and cerebrovascular malformations.

Resolution of hereditary hemorrhagic telangiectasia and anemia with prolonged alpha-interferon therapy for chronic hepatitis C

Hereditary hemorrhagic telangiectasia is a group of autosomal dominant disorders, characterized by telangiectases that develop in the skin, mucous membranes, and visceral organs. Currently, there is no satisfactory treatment of hereditary hemorrhagic telangiectasia. Interferon has never been used for the treatment of hereditary hemorrhagic telangiectasia. In this case, we report disappearance of hereditary hemorrhagic telangiectasia lesions after 12 months of treatment with interferon-alpha for chronic hepatitis C. Further studies are warranted to evaluate its role and potential use in the treatment of hereditary hemorrhagic telangiectasia.

Visceral manifestations in hereditary haemorrhagic telangiectasia type 2

Hereditary haemorrhagic telangiectasia (HHT) is a genetic vascular disorder characterised by epistaxis, telangiectases, and visceral manifestations. The two known disease types, HHT1 and HHT2, are caused by mutations in the endoglin (ENG) and ALK-1 genes, respectively. A higher frequency of pulmonary arteriovenous malformations (AVMs) has been reported for HHT1 while HHT2 is thought to be associated with a lower penetrance and milder disease manifestations. In this study, we present 10 families with an ALK-1 genotype. Visceral manifestations were detected in 24 (26%) of the 93 HHT2 patients from nine of the families and included gastrointestinal bleeding (14%), intrahepatic shunts (6%), and AVMs in the lung (4%) and brain (3%). Gastrointestinal bleeding, the most frequent visceral manifestation, was reported in six of the 10 families, mostly in patients over the age of 50. These patients also had frequent epistaxis and suffered from anaemia, often requiring blood transfusions. The identification of ALK-1 mutations in subjects with a suspected diagnosis and without clinical signs of HHT argue in favour of a molecular diagnosis. We also analysed the data published on 44 families with HHT2 and conclude that visceral manifestations occur in 26 of these families and affect 30% of HHT2 patients. This is considered an underestimate given incomplete and variable screening for lung, brain, and/or liver involvement in different clinical centres. These findings, however, stress the need for an early diagnosis of HHT that can be useful for the early control of associated visceral involvement.

Expression of the type III TGFbeta receptor during chick organogenesis

Transforming growth factor beta (TGFbeta) is a regulator of embryonic development. The role of specific TGFbeta receptors is emerging, and a unique role for the type III TGFbeta receptor (TBRIII) has been suggested. We report the pattern of TBRIII expression in chicken embryos from 2 to 14 days in ovo.

Disease-associated mutations in conserved residues of ALK-1 kinase domain

Activin receptor-like kinase-1 (ALK-1), the gene mutated in HHT type 2 (HHT2), is a serine/threonine kinase receptor type I of the TGF-beta superfamily, specifically expressed on endothelial cells. We established an HHT2 genotype in 16 families and report nine novel mutations. These include insertions and deletions of single base pairs in exons 3, 8 and 9, as well as nonsense mutations in exons 4 and 8 of ALK-1, which would lead to premature truncation and unstable mRNA or protein. Three novel missense mutations were identified in exons 7 and 8 of the kinase domain. Five previously reported substitutions were also observed in the families analyzed. Our results bring to 36, the number of mutations associated with HHT2, and are mostly found in exons 8 and 3 followed by exons 4 and 7. To ascertain the potential functional implications of the missense mutations in the ALK-1 kinase domain, we generated a model based on the three-dimensional structure of the homologous ALK-5 kinase domain. Our data reveal that the 11 missense mutations modify residues conserved among type I receptors and alter the polarity, charge, hydrophobicity and/or size of the substituted amino-acid and likely lead to misfolded and nonfunctional proteins.

Liver disease in hereditary hemorrhagic telangiectasia

Hereditary hemorrhagic telangiectasia (HHT), also known as Osler-Weber-Rendu disease, is an hereditary disorder that results in fibrovascular dysplasia with the development of telangiectasias and arteriovenous malformations. It predominantly involves the skin, mucous membranes, viscera, lungs, and brain. Hereditary hemorrhagic telangiectasia shows great genetic heterogeneity, and its phenotypes have been classified based on the recently identified mutated genes: endoglin (HHT-1) and activin-like kinase receptor-1 (HHT-2). Other families with phenotypic HHT do not bear these mutations; therefore, other genes are probably involved as well. Liver involvement is reported in up to 30% of persons affected by HHT. Large arteriovenous malformations in the liver can lead to significant complications, including high-output congestive heart failure, portal hypertension, hepatic encephalopathy, biliary ischemia, and liver failure. Embolization of large arteriovenous malformations in the liver remains controversial; however, liver transplantation can successfully eradicate these complications.

Percutaneous transluminal embolization with coils-treatment of pulmonary arteriovenous malformations

The clinical values of coils embolization in the treatment of pulmonary arteriovenous malformations (PAVM) and related complications were investigated. Eleven patients with PAVMs verified by pulmonary arterial angiography were treated by transcatheter coils embolization. Chest X-ray (11 cases), computer tomography (7 cases) and/or magnetic resonance imaging (2 cases) were performed before embolization. Blood-gas analysis was done in 5 cases before and after embolization. The follow-up materials of 8 patients were collected to evaluate the effect of embolization with coils. The clinical manifestations included cerebral embolus, hemoptysis and decreased oxygenation in 9 patients and the remaining 2 had no symptoms. 9/11 cases were found by chest X-ray and 8 were diagnosed definitely. 7/7, 2/2 cases were diagnosed by CT or MR and diagnosis was made in all cases. Embolization was performed in 29 vessels. Partial pressure of oxygen in arterial blood of 5 cases changed significantly before and after embolization. Slight complications occurred in 6 patients, such as low fever, chest pain, pleurisy. The follow-up results showed that 7 cases were cured effectively. No primary and secondary device migration, and no medical paradoxical embolization occurred. It was concluded that coils embolization is a well-established method for treating PAVMs. It is a minimally invasive lung preserving treatment with high efficiency and less complication.

[Rendu-Osler-Weber disease. Descriptive study of 17 cases]

OBJECTIVE

To study the prevalence and presentation forms of hereditary hemorrhagic telangiectasia (HHT) among the population in our hospital area.

MATERIALS AND METHODS

Descriptive, retrospective study of patients with the diagnosis of HHT from to 1999 at La Fe Hospital, Valencia. Family history, repeated epistaxis, mucocutaneous telangiectasis and visceral lesions, as well as administered treatments, and clinical course were evaluated.

RESULTS

Seventeen patients were diagnosed during such time period, with ages ranging from 23 to 80 years. Eight patients had family histories. The most common symptoms included epistaxis and iron-deficiency anemia, followed by muco-cutaneous telangiectasis. Six patients had neurological, five pulmonary, five gastrointestinal, and three hepatic manifestations, usually secondary to vascular malformations at those levels.

CONCLUSIONS

The prevalence of the disease maybe higher than previously reported. This disease should be considered in patients with repeated epistaxis and/or iron-deficiency anemia. The presence of telangiectasis that can suggest the diagnosis should be investigated. An early diagnosis of HHT can be useful for the early control of associated visceral malformations. Treatment of HHT should be tailored according to the clinical manifestations of the patient.

Hereditary haemorrhagic telangiectasia (Osler-Weber-Rendu syndrome): otorhinolaryngological manifestations

Hereditary haemorrhagic telangiectasia (HHT) is an autosomal dominant disorder affecting blood vessels of the skin, mucous membrane and viscera. The otorhinolaryngologist is the commonest clinician involved in management as epistaxis occurs in 93% of the patients. As marked advances have recently been made regarding the pathogenesis and management of the condition, the otorhinolaryngological perspective is reviewed.

Mutations in the ALK-1 gene and the phenotype of hereditary hemorrhagic telangiectasia in two large Danish families

Mutations in the ENG gene on chromosome 9 (HHT 1) and in the ALK-1 gene on chromosome 12 (HHT 2) have been reported as causes of hereditary hemorrhagic telangiectasia (HHT). HHT 1 has been correlated with a higher prevalence of pulmonary arteriovenous malformations than HHT 2. Other distinct phenotype-genotype correlations have not been described. The prevalence of HHT in the county of Fyn, Denmark, was 15.6 per 100,000 on January 1, 1995. All living patients and their first-degree relatives were invited to attend a detailed clinical examination and blood was drawn for mutation analysis. In two families mutations were identified in exon 8 of the ALK-1 gene. In family 6 we found a T1193A mutation. In this family a high prevalence of PAVM and severe GI bleeding was documented, while in family 8 with a C1120T mutation no individuals with PAVM were identified and only one patient had a history of severe GI bleeding. No mutations in the endoglin locus were found in either family.

Prevalence of pulmonary arteriovenous malformations (PAVMs) and occurrence of neurological symptoms in patients with hereditary haemorrhagic telangiectasia (HHT)

BACKGROUND

Hereditary haemorrhagic telangiectasia (HHT) is a dominantly inherited disease. HHT is characterized by a wide variety of clinical manifestations, including pulmonary arteriovenous malformations (PAVMs) and neurological symptoms.

OBJECTIVE

To estimate (i) the prevalence of PAVM, and (ii) the occurrence of neurological symptoms in a geographical well-defined population of HHT patients.

METHODS

HHT family members were invited to a clinical examination including registration of HHT manifestations, screening for pulmonary arteriovenous malformations and neurological evaluation. Two groups served as controls: (i) first-degree relatives without any signs of HHT; and (ii) age- and gender-matched controls.

SETTING

Odense University Hospital.

SUBJECTS

HHT patients identified in a cross-sectional family survey carried out in the County of Fyn, Denmark.

RESULTS

Included in the study were 169 HHT family members representing 24 families. They included both HHT patients and their first-degree relatives. The criteria of HHT were fulfilled in 75 participants; of these, 59 had a screening procedure performed, and PAVMs were demonstrated at pulmonary angiography (PA) in 18. Seven of the HHT patients had a history of cerebral stroke, compared with none of their healthy first-degree relatives.

CONCLUSION

The prevalence of PAVM was 24% amongst HHT patients. The study confirmed an increased prevalence of neurological symptoms amongst HHT patients; the odds ratio was estimated to be 7.6. In order to enable prevention of these complications, screening for PAVM should become an integral part of the medical care for HHT patients.

Clinical manifestations in a large hereditary hemorrhagic telangiectasia (HHT) type 2 kindred

HHT type 2 (HHT 2) is a multi-system vascular dysplasia caused by a mutation in the ALK-1 gene, but the phenotype has not been well defined. We report on 51 members of an HHT 2 kindred with an ALK-1 gene mutation shown to be associated with the disorder. This ALK-1 mutation was detected in 38 kindred members who were evaluated systematically for associated vascular abnormalities. Pulmonary arteriovenous malformations (AVMs) were found in 6% of those screened, cerebral AVM in 7%, hepatic AVM in 17%, and spinal AVM in 3%. We discuss these and other findings in the 38 affected kindred members, as well as findings in the 13 kindred members in whom the mutation was not detected. This study shows that pulmonary, cerebral, spinal, and hepatic AVMs can all occur in HHT 2. It also adds to the evidence suggesting that pulmonary AVMs are more common in HHT 1 than in HHT 2. We identify a higher prevalence of hepatic AVMs than previously reported in either HHT 1 or 2. This may be specific to the mutation in this kindred, but probably reflects the lack of routine screening for this manifestation. Even in this family in which all affected individuals have the same mutation, the clinical manifestations of HHT and their severity varied tremendously. Intrafamilial variation in expression of HHT is clearly significant, emphasizing the difficulty in establishing the diagnosis in individuals and in sub-typing families when DNA testing is not available.

Mutation and expression analysis of the endoglin gene in hereditary hemorrhagic telangiectasia reveals null alleles

Hereditary Hemorrhagic Telangiectasia (HHT) is an autosomal dominant disorder characterized by multisystemic vascular dysplasia and recurrent hemorrhage from the sites of vascular lesions. Two genes have been identified for HHT. Endoglin, a TGF-beta binding protein which maps to chromosome 9q3, is the gene for HHT1. The type and location of most of the previously described mutations in the endoglin (ENG) gene suggested a dominant-negative model of receptor-complex dysfunction for the molecular basis of this disorder. In this article we describe 11 novel ENG mutations in HHT kindreds, which include missense and splice-site mutations. Two identical missense mutations in unrelated families disrupt the start codon of the gene. In addition, some frameshift and nonsense mutations lead to very low or undetectable levels of transcript from the mutant allele. These combined data suggest that the nature of most ENG mutations is to create a null (nonfunctional) allele, and that there is no requirement for the synthesis of a truncated endoglin protein in the pathogenesis of HHT.

Identification of hereditary hemorrhagic telangiectasia type 1 in newborns by protein expression and mutation analysis of endoglin

Hereditary hemorrhagic telangiectasia (HHT) is a dominantly inherited vascular disorder that is heterogeneous in terms of age of onset and clinical manifestations. Endoglin is the gene mutated in HHT1, which is associated with a higher prevalence of pulmonary arteriovenous malformations than HHT2, where ALK-1 is the mutated gene. Endoglin is constitutively expressed on endothelial cells and inducible on peripheral blood activated monocytes so that protein levels can be measured by metabolic labeling and immunoprecipitation. We report the analysis of umbilical vein endothelial cells in 28 newborns from 24 families with a clinical diagnosis of HHT. Reduced levels of endoglin were observed in umbilical vein endothelial cells in 15/28 subjects and in activated monocytes of all clinically affected relatives tested, suggesting that these individuals had HHT1. No mutant protein was expressed at the cell surface in any of these cases, and a transient intracellular species was seen in samples of only two families, supporting a haploinsufficiency model. Quantitative multiplex PCR fragment analysis was established for the endoglin gene and revealed six mutations that were confirmed by automated DNA sequencing. An additional 10 mutations were identified in newborns by sequencing all exons. Of the 16 mutations, 10 were novel, three had been independently identified in related families, and three were previously known. Our data confirm that endoglin levels correlate with the presence or absence of mutation in HHT1 families, allowing the early identification of affected newborns that should be screened clinically to avoid serious complications of this disorder, such as cerebral arteriovenous malformations.

A murine model of hereditary hemorrhagic telangiectasia

Endoglin (CD105), an accessory protein of the TGF-beta receptor superfamily, is highly expressed on endothelial cells. Hereditary hemorrhagic telangiectasia type 1 (HHT1) is associated with mutations in the Endoglin gene, leading to haploinsufficiency. To generate a disease model and ascertain the role of endoglin in development, we generated mice lacking 1 or both copies of the gene. Endoglin null embryos die at gestational day 10.0-10.5 due to defects in vessel and heart development. Vessel formation appears normal until hemorrhage occurs in yolk sacs and embryos. The primitive vascular plexus of the yolk sac fails to mature into defined vessels, and vascular channels dilate and rupture. Internal bleeding is seen in the peritoneal cavity, implying fragile vessels. Heart development is arrested at day 9.0, and the atrioventricular canal endocardium fails to undergo mesenchymal transformation and cushion-tissue formation. These data suggest that endoglin is critical for both angiogenesis and heart valve formation. Some heterozygotes, either with an inbred 129/Ola or mixed C57BL/6-129/Ola background, show signs of HHT, such as telangiectases or recurrent nosebleeds. In this murine model of HHT, it appears that epigenetic factors and modifier genes, some of which are present in 129/Ola, contribute to disease heterogeneity.

Hereditary haemorrhagic telangiectasia: a population-based study of prevalence and mortality in Danish patients

INTRODUCTION

Hereditary haemorrhagic telangiectasia (HHT) is a dominantly inherited disease characterized by telangiectatic lesions. The disease manifestations are variable and include epistaxis, gastrointestinal bleeding, pulmonary arteriovenous malformations and cerebral arteriovenous malformations. Early death due to these complications has been described.

DESIGN

We report a study on the prevalence and mortality of HHT in a Danish population based on two cross-sectional surveys in combination with a long-term follow-up study.

SETTINGS AND SUBJECTS

Prevalent cases of HHT as of 1 January 1974 in the County of Fyn, Denmark, were identified. In 1995-97 a follow-up study of mortality was performed of the initial patient sample, and a new point prevalence rate of HHT as of 1 January 1995 was calculated. All live patients and their families were invited to attend a detailed clinical examination.

RESULTS

The prevalence of HHT in the County of Fyn was 13.8 per 100,000 on 1 January 1974 and 15.6 per 100,000 on 1 January 1995. In the HHT group as a whole, we found a slightly increased mortality; however, amongst the HHT patients younger than 60 years at inclusion the mortality of HHT patients was twice the expected. The excess mortality could be fully explained by severe HHT symptoms.

CONCLUSION

This study suggests that HHT is more prevalent than previously believed. In young patients the disease is associated with an excess mortality which is fully attributable to HHT. Future research should aim at the identification of HHT patients at particular risk of developing severe complications.

Liver transplantation as definitive therapy for complications after arterial embolization for hepatic manifestations of hereditary hemorrhagic telangiectasia

Experience with hepatic artery embolization for the treatment of symptomatic hepatic arteriovenous malformations (AVMs) in Rendu-Osler-Weber disease is limited. We report 2 cases of hepatic AVMs that caused mesenteric angina-like symptoms that were treated with embolization. Both patients developed parenchymal and bile duct necrosis, intrahepatic bilomas, and refractory biliary sepsis, subsequently leading to liver failure. We hypothesize that the pathophysiological cause of biliary necrosis in this setting is similar to that which occurs in the setting of hepatic artery thrombosis of the liver allograft. Progressive liver failure in these patients was treated successfully by liver transplantation. Liver transplantation offers definitive therapy by removing the source of ongoing sepsis, restoring normal liver function, and eliminating the intrahepatic AV shunt.

Mutant endoglin in hereditary hemorrhagic telangiectasia type 1 is transiently expressed intracellularly and is not a dominant negative

Endoglin (CD105), a component of the TGF-beta 1 receptor complex, is the target gene for the dominantly inherited vascular disorder hereditary hemorrhagic telangiectasia type 1 (HHT1). We have identified a novel endoglin splice site mutation, leading to an in-frame deletion of exon 3, in a new-born from a family with HHT. Expression of normal and mutant endoglin proteins was analyzed in umbilical vein endothelial cells from this baby and in activated monocytes from the affected father. In both samples, only normal dimeric endoglin (160 kD) was observed at the cell surface, at 50% of control levels. Despite an intact transmembrane region, mutant protein was only detectable by metabolic labeling, as an intracellular homodimer of 130 kD. In monocytes from three clinically affected HHT1 patients, with known mutations creating premature stop codons in exons 8 and 10, surface endoglin was also reduced by half and no mutant was detected. Overexpression into COS-1 cells of endoglin cDNA truncated in exons 7 and 11, revealed their intracellular expression, inability to be secreted and to form heterodimers at the cell surface. These results indicate that mutated forms of endoglin are transiently expressed intracellularly and not likely to act as dominant negative proteins, as proposed previously. A reduction in the level of functional endoglin is thus involved in the generation of HHT1, and associated arteriovenous malformations.