A hereditary haemorrhagic telangiectasia family with pulmonary involvement is unlinked to the known HHT genes, endoglin and ALK-1

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

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

Pulmonary hypertension in hereditary hemorrhagic telangiectasia: A clinical review

Hereditary hemorrhagic telangiectasia (HHT) is a rare autosomal dominant hereditary disorder characterized by recurrent spontaneous epistaxis, mucocutaneous telangiectasias, and solid organ arteriovenous malformations (AVMs). Pulmonary hypertension (PH) is an increasingly recognized complication in patients with HHT, most often precipitated by high-output heart failure in the presence of hepatic AVMs as well as pulmonary arterial hypertension in the form of a proliferative vasculopathy. The presence of PH in patients with HHT is associated with significant elevations in rates of morbidity and mortality. Additionally, there is growing recognition of a thromboembolic propensity in this population that increases the risk of chronic thromboembolic PH, posing unique clinical considerations regarding the use of anticoagulation. Patients with HHT are also at risk of PH due to disorders commonly seen in the general population, including left-sided heart and lung disease. The etiology of PH in HHT is multifaceted and complex; the diagnostic approach and treatment strategies must consider the underlying pathophysiology of HHT. This comprehensive review summarizes current knowledge of PH in HHT, detailing the pathogenesis of known etiologies, diagnostic evaluation, and suggested treatment modalities as well as emerging therapies that may be of future interest.

A Rare Case of Hereditary Hemorrhagic Telangiectasia: A Case Report

Hereditary hemorrhagic telangiectasia (HHT), also known as Osler-Weber-Rendu syndrome, is a very rare autosomal dominant genetic disorder that leads to abnormal blood vessel formation in the skin, mucus membranes (called telangiectasia), and organs such as the lung, liver, and brain. It occurs due to a mutation in one of the ACVRL1, ENG, and SMAD4 genes, which code for the formation of blood vessels. The most common symptom is recurring nosebleed (epistaxis; due to rupture of nasal mucosal telangiectasia), which begins in childhood and affects about 90-95% of people with HHT. Other common signs and symptoms include punctate, linear, or splinter-like telangiectasias on the upper body, oral mucosa, or nail beds, gastrointestinal bleeding, and iron deficiency anemia. The diagnostic criteria currently in use are the Curaçao criteria. The diagnosis is made by clinical screening (e.g., history and physical exam), baseline investigations (complete blood count, hemoglobin, hematocrit, and ferritin level), genetic testing, and detailed medical imaging to detect visceral arteriovenous malformations (AVMs) such as esophagogastroduodenoscopy, colonoscopy, multiphase contrast CT, computed tomography angiography (CTA or CT Angio), magnetic resonance angiography (MRA), chest X-ray, Doppler ultrasonography, liver biopsy, and cerebral angiography. Management includes intravenous iron therapy or blood transfusion, antifibrinolytics (e.g tranexamic acid), ablation therapies (e.g. laser treatment, radiofrequency ablation, electrosurgery, sclerotherapy, and argon plasma coagulation), and systemic anti-angiogenic agents (e.g. thalidomide, bevacizumab). In this report, we present the case of a 22-year-old man from Swabi, Pakistan, with a history of recurrent epistaxis (nosebleed) from childhood, who presented with multiple episodes of melena (blood in stool), fatigue, palpitation, and iron deficiency anemia for five years. Multiple esophagogastroduodenoscopies (OGDs) and colonoscopies were done over the years, which showed AVM in the antrum and fundus of the stomach, duodenum, and colon, and a diagnosis of HHT was made. CTA and exploratory laparotomy showed ileal loop hemangiomas. He was managed with multiple blood transfusions, argon plasma coagulation (APC) for the AVMs, oral thalidomide, and steroids. Despite therapy, the patient had intermittent episodes of blood in stool and low blood counts. During his stay in Hayatabad Medical Complex (HMC), the patient was managed with high-frequency blood transfusion and bevacizumab (systemic anti-angiogenic agent). A dramatic reduction in the number of required transfusions and improvement in the patient's bloodlines and symptoms was noted. This case highlights the importance of endoscopic methods for the timely diagnosis of HHT and its management with intravenous bevacizumab.

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

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

Thalamic abscess in a patient with hereditary hemorrhagic telangiectasia successfully treated with an empiric antibiotic regime: case report and review of the literature

BACKGROUND

Hereditary hemorrhagic telangiectasia (HHT) is a rare autosomal dominant disease associated with neurological complications, including cerebral abscesses (CA). They tend to be unique, supratentorial and lobar. While the surgical intervention is a rule of thumb when treating and diagnosing the etiology of these lesions, this is not always possible due to dangerous or inaccessible locations. We report the case of a patient solely treated with empiric antibiotics without stereotaxic intervention and satisfactory results.

CASE PRESENTATION

We present the case of a 21-year-old patient with a right thalamic abscess due to HHT and pulmonary arteriovenous malformations, previously embolized, treated solely with antibiotics. At first, we contemplated the possibility of a stereotaxic biopsy, but the high-risk location and the fact that our patient received a previous full course of antibiotic treatment (in another center), made us discard this intervention because of the low diagnostic yield. We started an empiric antibiotic regime. We followed up very closely the clinical and radiological evaluation the next weeks, adjusting our antibiotic treatment when necessary. The results were favorable from both the radiological and clinical aspects and 6 months after the diagnosis the images show its almost complete disappearance.

CONCLUSION

Carefully tailored antibiotic-only regime and vigilance of its adverse effects and close radiological following is a good treatment approach when surgery is not an option.

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.

Prenatal care and labor in patients with mesenchimal dysplasias (Marfan syndrome, Ehlers-Danlos syndrome, hereditary hemorrhagic telangiectasia)

Background: Mesenchymal dysplasias or inherited connective tissue diseases are the group of diseases with deficiency of various components of connective tissue. Connective tissue disorders can affect different organs: skeleton, sight organ, skin, lungs, heart. But the most dangerous is vascular wall insufficiency leading to high risk of hemorrhage, especially during pregnancy and delivery due to hemodynamic and hormonal effects on the walls of the modified vessels.Aim: To evaluate the risk of complications during the pregnancy and delivery in patients with mesenchymal dysplasias.Study design: Fifty-six pregnancies in patients with mesenchymal dysplasias, including subclinical forms of diseases: 23 with Marfan syndrome (I group), 22 with Ehlers-Danlos syndrome (II group), and 11 with Osler-Weber-Rendu syndrome (hereditary hemorrhagic telangiectasia) (III group) of the age from 18 to 36. The study included retrospective analysis (for the period from 1993 to 2005) and prospective study. Results of study showed high risk of life-threatening complications during pregnancy and delivery, especially the risk of hemorrhage and cardiovascular complications. In all the patients, we observed the progression of bleeding or development of bleeding in new localizations (epistaxis in 27 patients, easy brushing in 22, skin and mucosa telangiectasia in 20, gastrointestinal bleedings in 4, hemoptysis in 4, hematomas for minor traumas in 14, conjunctivas hemorrhages in 5).Conclusion: The pathogenesis of bleeding in such patients has mixed pattern: besides vascular wall pathology coagulation deficiency plays some role. The preferred delivery method for such patients is caesarean section. Deep vaginal ruptures and serious hemorrhage accompany vaginal delivery.

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

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99mTc-MAA Pulmonary Scintigraphy in Hereditary Hemorrhagic Telangiectasia

A 5-year-old boy was admitted due to shortness of breath. Blood gas analysis showed hypoxemia. However, thoracic and abdominal CT, brain MRI, and MR angiography were all normal. A Tc-MAA pulmonary scintigraphy revealed right-to-left shunting of the blood. Further genetic analysis showed the mutations in the activin receptor-like kinase 1 gene, and a diagnosis of hereditary hemorrhagic telangiectasia was made.

Functional analysis of endoglin mutations from hereditary hemorrhagic telangiectasia type 1 patients reveals different mechanisms for endoglin loss of function

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant inheritable vascular dysplasia caused by mutations in genes encoding either endoglin or activin receptor-like kinase-1 (ALK1). Functional significance of endoglin missense mutations remains largely unknown leading to a difficult discrimination between polymorphisms and pathogenic mutations. In order to study the functional significance of endoglin mutations and to help HHT1 diagnosis, we developed a cellular assay based on the ability of endoglin to enhance ALK1 response to bone morphogenetic protein 9 (BMP9). We generated and characterized 31 distinct ENG mutants reproducing human HHT1 missense mutations identified in patients of the Molecular Genetics Department in Lyon. We found that 16 mutants behaved like wild-type (WT) endoglin, and thus corresponded to benign rare variants. The 15 other variants showed defects in BMP9 response and were identified as pathogenic mutations. Interestingly, two mutants (S278P and F282V) had lost their ability to bind BMP9, identifying two crucial amino acids for BMP9 binding to endoglin. For all the others, the functional defect was correlated with a defective trafficking to the cell surface associated with retention in the endoplasmic reticulum. Further, we demonstrated that some intracellular mutants dimerized with WT endoglin and impaired its cell-surface expression thus acting as dominant-negatives. Taken together, we show that endoglin loss-of-function can result from different mechanisms in HHT1 patients. We also provide a diagnostic tool helping geneticists in screening for novel or conflicting ENG mutations.

Connective tissue disorders and cardiovascular complications: the indomitable role of transforming growth factor-beta signaling

Marfan Syndrome (MFS) and Loeys-Dietz Syndrome (LDS) represent heritable connective tissue disorders that cosegregate with a similar pattern of cardiovascular defects (thoracic aortic aneurysm, mitral valve prolapse/regurgitation, and aortic root dilatation with regurgitation). This pattern of cardiovascular defects appears to be expressed along a spectrum of severity in many heritable connective tissue disorders and raises suspicion of a relationship between the normal development of connective tissues and the cardiovascular system. Given the evidence of increased transforming growth factor-beta (TGF-β) signaling in MFS and LDS, this signaling pathway may represent the common link in this relationship. To further explore this hypothetical link, this chapter will review the TGF-β signaling pathway, heritable connective tissue syndromes related to TGF-β receptor (TGFBR) mutations, and discuss the pathogenic contribution of TGF-β to these syndromes with a primary focus on the cardiovascular system.

Juvenile polyposis, hereditary hemorrhagic telangiectasia, and early onset colorectal cancer in patients with SMAD4 mutation

BACKGROUND

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant disorder most often caused by mutation in the endoglin or ALK1 genes. A distinct syndrome combines the clinical features of HHT and juvenile polyposis (JP) and has been associated with SMAD4 mutation. The aim of this study was to describe the phenotype of patients with JP-HHT and SMAD4 mutations and to compare this phenotype with HHT or JP patients with mutations other than SMAD4.

METHODS

Patients prospectively enrolled in the Toronto HHT and JP databases who underwent genotyping were included. The phenotypic characteristics of JP-HHT patients with SMAD4 mutations and patients with mutations other than SMAD4 were analyzed and compared.

RESULTS

Three hundred and fifty-eight patients underwent genetic testing (HHT, n = 332; JP, n = 26). Among fourteen patients identified with SMAD4 mutations, ten met the clinical diagnostic criteria for both JP and HHT (71%). Patients with SMAD4 mutations had 100% penetrance of the polyposis phenotype. All patients with JP and SMAD4 mutation had features of HHT. Three JP-HHT patients developed early onset colorectal cancer (CRC) (mean age 28 years). JP-HHT patients with SMAD4 mutation had a significantly higher rate of anemia than HHT patients with mutations other than SMAD4.

CONCLUSIONS

Patients with HHT and SMAD4 mutations are at significant risk of JP and CRC. The gastrointestinal phenotype is similar to JP patients without SMAD4 mutation. It is essential for HHT patients to undergo genetic testing to determine if they have SMAD4 mutations so that appropriate gastrointestinal screening and surveillance for JP and CRC can be completed.

The molecular genetics and cellular mechanisms underlying pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is an incurable disorder clinically characterised by a sustained elevation of mean arterial pressure in the absence of systemic involvement. As the adult circulation is a low pressure, low resistance system, PAH represents a reversal to a foetal state. The small pulmonary arteries of patients exhibit luminal occlusion resultant from the uncontrolled growth of endothelial and smooth muscle cells. This vascular remodelling is comprised of hallmark defects, most notably the plexiform lesion. PAH may be familial in nature but the majority of patients present with spontaneous disease or PAH associated with other complications. In this paper, the molecular genetic basis of the disorder is discussed in detail ranging from the original identification of the major genetic contributant to PAH and moving on to current next-generation technologies that have led to the rapid identification of additional genetic risk factors. The impact of identified mutations on the cell is examined, particularly, the determination of pathways disrupted in disease and critical to pulmonary vascular maintenance. Finally, the application of research in this area to the design and development of novel treatment options for patients is addressed along with the future directions PAH research is progressing towards.

[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.

Anesthetic implications for the parturient with hereditary hemorrhagic telangiectasia

PURPOSE

To review the effects of hereditary hemorrhagic telangiectasia (HHT) in the parturient and the anesthetic management of such patients during pregnancy and delivery.

SOURCE

A literature search (1966-2008) was performed using Medline and EMBASE databases. Bibliographies of retrieved articles were searched for additional sources.

PRINCIPAL FINDINGS

Hereditary hemorrhagic telangiectasia affects 1 in 5000-8000 people. It is a genetic condition in which vascular dysplasia affects many organs particularly the pulmonary, cerebral, gastrointestinal, and spinal vasculature. A large proportion of women with HHT have uneventful pregnancies. However, women can present in pregnancy with clinically silent but potentially life-threatening features of the disorder including fatal hemorrhage from ruptured arteriovenous malformations (AVMs), systemic emboli, and high output cardiac failure secondary to arteriovenous shunting. Literature on the anesthetic management of HHT in pregnancy is limited. Both general and regional anesthetic techniques have been successfully performed in these patients, but are reliant on identifying the presence of specific AVMs; avoidance of cardiovascular instability; and prophylaxis against systemic emboli secondary to pulmonary AVM shunting. The presence of spinal AVMs is considered a relative contraindication to regional techniques. As with other systemic AVMs, these can develop and increase in size during pregnancy with implications for the timing of screening and surveillance.

CONCLUSIONS

An understanding of the presence and potential development of life-threatening AVMs during pregnancy is imperative for anesthesiologists caring for parturients with HHT. Even in the asymptomatic patient, a high index of suspicion should be maintained, screening performed where possible and anesthetic technique adapted accordingly.

Hereditary hemorrhagic telangiectasia with multiple hepatic and pulmonary nodular lesions

A 50-year-old female visited the hospital for further evaluation of multiple pulmonary and hepatic nodules. First, she visited her primary physician for general fatigue due to anemia. She had recurrent epistaxis, and her mother had suffered from hereditary hemorrhagic telangiectasia (HHT). Telangiectasias were present in the stomach. This patient was diagnosed with HHT. Computed tomography (CT) revealed multiple pulmonary and hepatic nodules. The pulmonary nodules were due to bleeding from arteriovenous malformations of the lung. Abdominal CT and angiography showed a dilated and meandering hepatic artery, arteriovenous shunts and multiple hepatic nodules. Gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (MRI) showed enhancement in the early dynamic phase and in the liver-specific phase. A liver tumor biopsy of a hepatic nodule showed nodular regenerative hyperplasia (NRH). This report presents a case of HHT with multiple pulmonary and hepatic nodular lesions. Gd-EOB-DTPA-enhanced MRI was useful for making a diagnosis of NRH.

Brain abscess and hereditary hemorrhagic telangiectasia

Hereditary hemorrhagic telangiectasia (HHT) is a rare autosomal dominant disorder that can lead to serious central nervous system complications including hemorrhage, ischemia, and infection. Symptoms can be mild, making diagnosis problematic. Fifty-three prior cases of HHT and brain abscess are described, in addition to two new cases. The clinical manifestations and current methods for diagnosis and management of patients with HHT are reviewed. Early recognition of HHT is important because screening in these patients and affected family members may help prevent complications. In addition, advancements in imaging, surgical techniques, antibiotics, and genetic testing may improve outcomes.

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.

Pulmonary nodular opacities in children with hereditary hemorrhagic telangiectasia

BACKGROUND

Hereditary hemorrhagic telangiectasia (HHT) is a rare inherited disorder of vascular endothelium that can result in the formation of pulmonary arteriovenous malformations (pAVMs). We observed that small pulmonary nodules, possibly representing early vascular malformations, are more common in these children than in the general population.

OBJECTIVE

To describe and characterize the small pulmonary nodules seen on chest CT examination in the lungs of children with HHT.

MATERIALS AND METHODS

We followed 19 children who had undergone chest CT as part of their initial diagnostic evaluation in the HHT clinic of a pediatric hospital. Chest CT scans were reviewed independently by two radiologists blinded to clinical data. Pulmonary nodules were analyzed according to lobar distribution, anatomic position in the lung (outer, mid, inner third), shape (round, linear, V- or Y-shaped, ill-defined), presence of overt AVMs, and nodule size (<or= or >5 mm). We also reviewed a control group of chest CT scans performed on 25 age-matched children.

RESULTS

A total of 35 pulmonary nodules were identified on the CT scans in 15 of the 19 children. Multiple nodules were seen in eight children (42%), solitary nodules were seen in seven children (37%) and no nodules were seen in the remaining four children (21%). The nodules were found to be nonspecific with regard to multiple factors other than their anatomic position within the lung. The chest CT scans of 2 of the 25 age-matched controls revealed a total of only four nodules, a significantly lower total (P = 0.0001 vs. children with HHT).

CONCLUSION

Nonspecific nodules are commonly seen in children with HHT.

Liver involvement in hereditary hemorrhagic telangiectasia (HHT)

Liver involvement in hereditary hemorrhagic telangiectasia (HHT) consists of extensive intrahepatic vascular malformations associated with blood shunting (arteriovenous, arterioportal and/or portovenous). It is a rare disorder that nevertheless can result in significant systemic and hepatobiliary abnormalities. Although hepatic vascular malformations are present in a majority of patients with HHT, symptoms occur in a only a minority with a clear predominance for the female gender. Symptoms from liver vascular malformations are often misdiagnosed and this can lead to potentially harmful interventions. In this review article, clinical findings of liver involvement in HHT and their pathophysiology are discussed as well as diagnostic methodologies, therapies used and their outcome. Data presented is based on a review of the literature performed in October 2006 using the following MEDLINE search terms: (hereditary hemorrhagic telangiectasia [ALL] OR Rendu-Osler-Weber [ALL]) AND (liver OR hepatic [ALL]). Papers were considered if they were published in English and if they included specific cases that were sufficiently described.

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.

[Pulmonary arteriovenous malformations - association with hereditary hemorrhagic telangiectasia. Clinical cases and family screening]

Pulmonary arteriovenous malformations are a rare disorder associated to hereditary hemorrhagic telangiectasia in over 50 % of the cases. Clinical presentation, diagnostic work-up, therapeutic options and prognosis are reviewed by the authors. Pulmonary arteriovenous malformations are known to have considerable morbidity and mortality, their treatment being advisable as well as their screening among family members, especially if the index case is diagnosed with both pulmonary arteriovenous malformations and hereditary hemorrhagic telangiectasia. To this moment prospective studies establishing the best diagnostic work-up for the patients and their families are lacking. The authors report two pulmonary arteriovenous malformations cases in a family with hereditary hemorrhagic telangiectasia. Patient's diagnosis led to family screening which resulted in the identification of pulmonary arteriovenous malformations in two family members and pulmonary disease exclusion in four patients previously known to have hereditary hemorrhagic telangiectasia.

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.

A novel mutation in ALK-1 causes hereditary hemorrhagic telangiectasia type 2

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal-dominant bleeding disorder and has two variants, HHT1 and HHT2, associated with mutations in the ENG and ALK-1 genes, respectively. We identified one Chinese HHT2 family to investigate the pathogenic gene and its possible mechanism of action by mutation screening and functional study. One substitution mutation (1717C>T) in exon 10 of the ALK-1 was found by sequencing of all exons of ENG and ALK-1 and caused a R479X mutation in the ALK-1 protein. ALK-1 mRNA and plasma thrombomodulin were measured by real-time quantitative PCR and ELISA, respectively. There was no significant difference in the expression levels of ALK-1 mRNA between patients and healthy individuals. A significantly higher level of thrombomodulin was found in HHT patients. These findings indicate that the mutation causes truncation of the ALK-1 protein at the post-transcriptional level; the plasma thrombomodulin may provide an easy diagnostic indicator in HHT patients.

Hereditary Hemorrhagic Telangiectasia (HHT) in Dentistry: A Literature Review

Hereditary Hemorrhagic Telangiectasia (HHT) is an autosomal-dominantly-inherited vascular dysplasia characterized by age-dependant incomplete penetrance and variable expressivity, with clinical manifestations consisting in epistaxis, mucocutaneous telangiectases, gastrointestinal bleeding and arteriovenous malformations (AVMs), which affects approximately ½ million people world-wide. It affects males and females of all racial and ethnic groups. Up to 1/3 of HHT patients have multiple organ involvement, which can be disabling and/or life threatening. HHT can be treated successfully if correctly diagnosed. Morbidity of HHT is often due to complications of AVMs, such as stroke or haemorrhage, also known to occur in children. Many authors have reported successful new therapeutical options for AVMs, which have resulted in a significant decrease of life-threatening complications and HHT morbidity. Since early diagnosis permits an appropriate care of affected subjects, a very sensitive mutation screening technique is required to identify the mutation carriers among all at-risk individuals belonging to HHT-families. There may be one or more genes that cause HHT but, if so, they are quite rare. Currently, scientists are trying to better understand exactly how the abnormal gene can interfere with normal blood vessel formation and promote the phenotype of HHT, so that better treatments for the symptoms of HHT can be developed.

Variations in structural protein expression and endothelial cell proliferation in relation to clinical manifestations of cerebral cavernous malformations

OBJECTIVE

Cerebral cavernous malformations (CCMs) are associated with hemorrhagic proliferation of endothelial-lined vascular caverns, resulting in hemorrhagic stroke, epilepsy, and other neurological manifestations. We hypothesize that structural protein expression and endothelial cell proliferation markers within CCM lesions are different in the setting of various clinical manifestations.

METHODS

The percentage of immunohistochemically stained caverns positive for collagen IV, fibronectin, laminin, alpha-smooth muscle actin, myosin, and smoothelin and the percentage of dividing endothelial cells within caverns were determined in 36 excised CCM surgical specimens. These were compared in CCMs with different multiplicity, location, and size in patients of different age, sex, seizure status, and hemorrhage status.

RESULTS

Comparisons of seven lesion features and clinical manifestations with the fraction of caverns containing the structural proteins studied and endothelial cell proliferation demonstrated no significant differences. A possible exception was the difference (P < 0.05) in the fraction (mean +/- standard deviation) of positively stained caverns for collagen IV between adult (0.63 +/- 0.39) and pediatric patients (0.87 +/- 0.21) as well as fewer caverns with laminin expression in older patients. These trends did not sustain significance with Bonferroni's correction for multiple comparisons.

CONCLUSION

The fraction of caverns containing the particular structural proteins studied and endothelial cell proliferation within caverns are not correlated with particular lesion features and clinical manifestations that were investigated in CCMs. The possible fewer fractions of caverns containing collagen IV and laminin in adult lesions compared with pediatric lesions may have implications for lesion regression and quiescence with age.

The TGFβ activated kinase TAK1 regulates vascular development in vivo

TGFβ activated kinase 1 (TAK1) is a MAPKKK that in cell culture systems has been shown to act downstream of a variety of signaling molecules,including TGFβ. Its role during vertebrate development, however, has not been examined by true loss-of-function studies. In this report, we describe the phenotype of mouse embryos in which the Tak1 gene has been inactivated by a genetrap insertion. Tak1 mutant embryos exhibit defects in the developing vasculature of the embryo proper and yolk sac. These defects include dilation and misbranching of vessels, as well as an absence of vascular smooth muscle. The phenotype of Tak1 mutant embryos is strikingly similar to that exhibited by loss-of-function mutations in the TGFβ type I receptor Alk1 and the type III receptor endoglin,suggesting that TAK1 may be a major effector of TGFβ signals during vascular development. Consistent with this view, we find that in zebrafish,morpholinos to TAK1 and ALK1 synergize to enhance the Alk1 vascular phenotype. Moreover, we show that overexpression of TAK1 is able to rescue the vascular defect produced by morpholino knockdown of ALK1. Taken together,these results suggest that TAK1 is probably an important downstream component of the TGFβ signal transduction pathway that regulates vertebrate vascular development. In addition, as heterozygosity for mutations in endoglin and ALK1 lead to the human syndromes known as hereditary hemorrhagic telangiectasia 1 and 2, respectively, our results raise the possibility that mutations in human TAK1 might contribute to this disease.

Echocardiographic screening discloses increased values of pulmonary artery systolic pressure in 9 of 68 unselected patients affected with hereditary hemorrhagic telangiectasia

BACKGROUND

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant disorder characterized by the presence of telangiectases and arteriovenous malformations. In some families in whom a form of idiopathic pulmonary arterial hypertension cosegregated with HHT, mutations in the ACVRL1 gene were present.

PURPOSE

We noninvasively measured the pulmonary artery systolic pressure (PASP) in a group of patients with HHT.

METHODS

Doppler transthoracic echocardiography and mutation analysis by direct sequencing were used.

RESULTS

We studied 68 patients (age 19-84 years, mean 50.75 + 15.11; 32 females) and PASP measurement was possible in 44 (64. 7%); in addition, 9 of them (20.5%) showed elevated values. Molecular analysis identified mutations in the ACVRL1 gene in 7 of these 9 subjects. Even on exclusion of relatives of the single case with known pulmonary hypertension, 5 of 37 patients (13.5%) still showed values higher than those of controls.

CONCLUSION

The data indicate that elevated PASP values are a frequent and previously unrecognized complication of HHT. Because clinically significant pulmonary artery hypertension (a relevant cause of morbidity and mortality) may subsequently develop in these patients, we propose that the measurement of PASP should be included among the parameters recorded for all patients undergoing Doppler transthoracic echocardiography during routine clinical screening.

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.

[Pulmonary vascular manifestations in hereditary hemorrhagic telangiectasia]

Hereditary hemorrhagic telangiectasia (Osler-Rendu-Weber disease) is a genetic disorder with autosomal dominance, variable penetrance, and an estimated prevalence of 1/10,000 inhabitants in France. Diagnosis is based on clinical criteria including epistaxis, telangiectasia, visceral manifestations, and familial occurrence. Pulmonary arteriovenous malformations, present in 15-33% of patients, are its primary visceral complications. The disease may be revealed by infectious and ischemic neurological manifestations due to paradoxical embolism. The high frequency of neurologic complications even in asymptomatic patients justifies systematic screening for pulmonary arteriovenous malformations. Treatment of these malformations is based on percutaneous transcatheter coil embolization of the feeding artery. Pulmonary arterial hypertension is rare in this disease. It may be due to systemic arteriovenous shunting in the liver, which increases cardiac output, or be similar to idiopathic pulmonary hypertension.

Capillaroscopy of the dorsal skin of the hands in hereditary hemorrhagic telangiectasia

BACKGROUND

Cutaneous telangiectases are manifestations of hereditary hemorrhagic telangiectasia (HHT), a dominantly inherited disorder. Telangiectases have been studied by skin biopsy, and recently by nailfold capillaroscopy.

AIM

To confirm the diagnostic role of nailfold capillaroscopy, and assess the value of skin capillaroscopy of the dorsum of the hands in HHT.

DESIGN

Prospective clinical investigation.

METHODS

Using a Wild Heerbrugg-M650 microscope, we studied the nailfolds and dorsum of the hands of 88 patients (37 females, 51 males, mean age 39.7 +/- 18.4 years), including 85 with positive genetic testing and three with clinical diagnosis (at least three clinical criteria but a negative genetic test) and 27 controls (13 females, 14 males, mean age 38.6 +/- 19.6 years).

RESULTS

Microscopic telangiectases were observed on the dorsum of the hands in 80/88 patients (91%): 77 with positive and three with negative genetic tests. No control showed vascular abnormalities. In six patients (7%), nailfold capillaroscopy showed pseudo-megacapillaries and megacapillaries; the remaining 82 (93%) and all controls, had normal capillaroscopic patterns.

DISCUSSION

HHT can induce morphological changes in microcirculation that are more easily detectable on the dorsum of the hands than in the nailfold. Microscopic lesions without macroscopic telangiectases were also noted, suggesting the need for further research. Capillaroscopy may provide an additional non-invasive diagnostic criterion for HHT.

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.

Hereditary hemorrhagic telangiectasia: ENG and ALK-1 mutations in Dutch patients

Hereditary hemorrhagic telangiectasia (HHT) or Rendu-Osler-Weber disease is an autosomal dominant disorder characterized by an aberrant vascular development. The resulting vascular lesions range from smaller mucocutaneous telangiectases to large visceral arteriovenous malformations, especially in the skin, lung, gastrointestinal tract and the brain. Mutations in the genes encoding endoglin (ENG, chromosome 9q34) and activin A receptor type-like kinase 1 (ALK-1, also named ACVRL1, chromosome 12q13) are associated with HHT1 and HHT2, respectively. We report here on the genetic and molecular heterogeneity found in the HHT population in the Netherlands. Probands of 104 apparently unrelated families were studied and we performed sequence analysis on both the ENG gene and ALK-1 gene. In most of the probands, we found a mutation in one of the two genes: 53% in the ENG gene and 40% in the ALK-1 gene. In 7% of the families no ENG or ALK1 mutation was found. The mutations detected were deletions, insertions, nonsense, missense and splice site mutations. The majority were novel mutations.

Does any lower gastrointestinal bleeding in patients suffering from hereditary hemorrhagic telangiectasia (Osler-Weber-Rendu) necessitate a full colonic visualization?

BACKGROUND

Hereditary hemorrhagic telangiectasia (HHT) (the Osler-Weber-Rendu syndrome) is a rare autosomal dominant disease characterized by telangiectasias and arteriovenous malformations of the upper and lower respiratory tract, gastrointestinal tract, skin and central nervous system. Several previous reports have documented the appearance of a concomitant neoplasm in patients with this syndrome.

AIMS

To study the occurrence and the clinical characterization of colonic neoplasm in patients with HHT.

METHODS

We retrospectively reviewed the computerized database of the Hadassah University Hospitals (Jerusalem, Israel) for all patients with the diagnosis of HHT between January 1st, 1980 and July 30th, 2002. Cases of neoplasm were documented by review of medical charts and pathology reports.

RESULTS

Six of the 24 patients developed malignancy. Three of the cases had extra colonic malignancy (melanoma in two patients and adenocarcinoma of urinary bladder in one patient) and three patients had adenocarcinoma of the colon. An additional three patients developed multiple colonic polyps (one patient had melanoma and one patient had adenocarcinoma of urinary bladder).

CONCLUSIONS

HHT may be associated with the development of colonic adenocarcinoma and polyps. Therefore, in patients with HHT who present with new-onset anemia or gastrointestinal bleeding a lower gastrointestinal tract evaluation should be performed, even if their blood loss is suspected to be a manifestation of gastrointestinal HHT.

Umbilical vein and placental vessels from newborns with hereditary haemorrhagic telangiectasia type 1 genotype are normal despite reduced expression of endoglin

Hereditary haemorrhagic telangiectasia, HHT, is an autosomal dominant disorder that affects approximately 1 in 8000 people. HHT1 is associated with mutations in the ENG (Endoglin) gene and with haploinsufficiency. The disorder is characterized by focally dilated vessels, which can lead to arteriovenous malformations and serious complications even in young children. In the current study, umbilical cord and placenta samples from newborns with ENG mutations were analyzed to estimate the level of corresponding protein and look for potential vascular dysplasia. We confirmed, using metabolic labelling and flow cytometry, that endoglin levels were significantly reduced to median values of 47 per cent (range 32-56 per cent) and 58 per cent (46-90 per cent), respectively, in human umbilical vein endothelial cells derived from newborns with ENG mutations (HHT1 group; n=18) relative to samples from newborns shown not to have the familial mutation (non-HHT group). We also quantified the relative expression of endoglin by estimating the endoglin/PECAM-1 staining ratio in tissue sections. We observed significantly lower values in the HHT1 group, compared to the non-HHT group for the umbilical vein (n=9; median 0.6 vs 0.9; ranges 0.2-1.0 and 0.5-1.5) and for placental stem villus vessels (n=9 and 10; median 0.42 vs 0.93; ranges 0.24-0.58 and 0.56-1.18). No differences in the estimated umbilical vein cross-sectional area and in the proportion of vessels present in placental villi were observed in sections from the HHT1 group relative to the non-HHT group. Thus, blood vessels from HHT1 individuals are maintained intact in the umbilical vein and placenta during pregnancy and delivery, despite a significant reduction in endoglin expression.

Hereditary Vascular Anomalies

Increased understanding of the mechanisms of angiogenesis and lymphangiogenesis has provided a glimpse at some of the molecules involved in the pathophysiology of hemangiomas and vascular malformations. This review focuses on recent advances in our understanding of the mechanisms of angiogenesis/lymphangiogenesis and the differentiation of arterial, venous, and lymphatic vessels. We integrate this knowledge with new data obtained from genetic studies in humans, which have revealed a number of heretofore-unsuspected candidates involved in the development of familial vascular anomalies. We present a common infantile vascular tumor, hemangioma, and then focus on hereditary familial vascular and lymphatic malformations. We also summarize transgenic mouse models for some of these malformations. It seems reasonable to believe that novel therapeutic strategies will soon emerge for the treatment of hemangiomas and vascular malformations.

Molecular screening of ALK1/ACVRL1 and ENG genes in hereditary hemorrhagic telangiectasia in France

Hereditary hemmorrhagic telangiectasia (HHT, or Osler-Rendu-Weber syndrome) is an autosomal dominant disease characterized by arteriovenous malformations, affecting 1 out of 10,000 individuals in France. The disease is caused by mutations of two genes: ENG and ALK1 (ACVRL1). We screened the coding sequence of ENG and ALK1 in 160 unrelated French index cases. A germline mutation was identified in 100 individuals (62.5%). A total of 36 mutations were found in ENG, including three nonsense mutations, 19 small insertions/deletions leading to a frameshift, two inframe deletions, seven missense mutations, and five intronic or splice-site mutations. Of the 36 mutations, 33 were novel mutations. A total of 64 mutations were found in ALK1, including six nonsense mutations, 28 small insertions/deletions leading to a frameshift, one inframe deletion, 27 missense mutations, and two intronic or splice-site mutations. Of the 64 mutations, 27 were novel mutations. Mutations were found in most parts of the coding sequence for both genes, except ALK1 exon 5 and ENG exons 12 to 14. Missense mutations in ALK1 were more frequent in exons 7, 8, and 10. ENG cDNA was sequenced for three intronic mutations: c.689+2T>C produced an abnormal transcript excluding exon 5, c.1103+3_1103+8del activated a cryptic splice site 22 bp upstream, and c.1428G>A produced two abnormal transcripts, one including intron 11 and the other excluding exon 10. Although most of the mutations were private, some recurrent mutations in ALK1 were of particular interest. Mutation c.1112_1113dupG (p.Gly371fsX391) was found in 17 unrelated individuals sharing a common haplotype, strongly suggesting a founder effect related to the concentration of patients previously reported in a specific French region (Rhône-Alpes). Three missense mutations involved the same codon: c.1231C>T (p.Arg411Trp), c.1232G>C (p.Arg411Pro), and c.1232G>A (p.Arg411Gln) were found in seven, two, and one patients, respectively. Haplotype analysis was in favor of both a founder effect and a mutation hot-spot.

Endoglin gene mutations and polymorphisms in Italian patients with hereditary haemorrhagic telangiectasia

Autosomal-dominant hereditary haemorrhagic telangiectasia (HHT) is a genetically heterogeneous disease caused by mutations in at least two different loci. We screened for mutations in four Italian families where segregation studies showed clear evidence of linkage to the endoglin (ENG) locus. In addition, one sporadic case and three patients with pulmonary arteriovenous malformations, belonging to small nuclear families unsuitable for linkage analysis, were included in the screening. The proband from each family was investigated using single-strand conformation polymorphism and heteroduplex analysis; potential variants were sequenced. Four novel and one previously reported mutation were detected, as well as three new polymorphisms. The novel mutations included deletions in exon 1 (patient 581/02), exon 5 (patient 780/01) and exon 7 (patient 700/01), and a C-->T229 substitution in exon 3 (patient 462/02). When analysing patient 700/01 and his affected daughter, we encountered a mutant ENG allele with two mutations--a deletion in exon 7 and a substitution in exon 12--which converts isoleucine 575 into threonine, in a non-conserved region. Both mutations were absent in the two healthy sons of the patient, while the polymorphic variant in exon 12 was present in his healthy father. These results and haplotype-segregation studies suggest that a de novo deletion had occurred in the gamete of paternal origin. For the first time the parental germline in which a de novo HHT mutation occurred has been identified.

Mouse model for hereditary hemorrhagic telangiectasia has a generalized vascular abnormality

BACKGROUND

Mutations in endoglin or activin like kinase-1, both involved in the endothelial transforming growth factor-beta signaling pathway, cause the autosomal dominant bleeding disorder hereditary hemorrhagic telangiectasia. We and others have reported mouse models for this disease that share the characteristic phenotype of dilated vessels and sporadic hemorrhage. The reasons for the variable phenotype in hereditary hemorrhagic telangiectasia are not understood.

METHODS AND RESULTS

After a detailed immunohistochemical analysis of 129/Ola mice, which are heterozygous for a targeted deletion in the endoglin gene, we observed intrinsic abnormalities in the vascular walls throughout the cutaneous vasculature. Postcapillary venules were dilated, and up to 70% of the vascular wall had no smooth muscle cells. The supporting layers of collagens and elastin were irregular, with thin areas, adding to the fragility of these vessels. A variable hemorrhagic phenotype was observed in which local bleeding is associated not only with fragile vessels but also with regions of inflammation.

CONCLUSIONS

These findings have relevance to our understanding of the molecular basis of vascular integrity in a wide range of diseases.

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.

Hereditary haemorrhagic telangiectasia (Osler-Weber-Rendu syndrome): a view from the 21st century

Hereditary haemorrhagic telangiectasia (HHT) affects one in 5-8000, and no longer can be viewed as solely causing anaemia (due to nasal and gastrointestinal bleeding) and characteristic mucocutaneous telangiectasia. Arteriovenous malformations commonly occur, and in the pulmonary and cerebral circulations demand knowledge of risks and benefits of asymptomatic screening and treatment. HHT is inherited as an autosomal dominant trait and there is no age cut off when apparently unaffected offspring of an individual with HHT can be told they are unaffected. This review focuses on the evolving evidence base for HHT management, issues regarding pregnancy and prothrombotic treatments, and discusses the molecular and cellular changes that underlie this disease.