Role of transthoracic contrast echocardiography in the clinical diagnosis of hereditary hemorrhagic telangiectasia

[Hereditary hemorrhagic telangiectasia]

Hereditary hemorrhagic telangiectasia, also known as Rendu-Osler - Weber disease, is a rare, autosomal dominant vascular disease, with prevalence of 1/5,000. The condition is characterized by muco-cutaneous telangiectasias, which are responsible for a hemorrhagic syndrome of variable severity, as well as arteriovenous malformations (AVMs) appearing in the lungs, the liver, and the nervous system. They can be the source of shunts, which may be associated with high morbidity (neurological ischemic stroke, brain abscess, high-output heart failure, biliary ischemia…). It is therefore crucial to establish a clinical diagnosis using the Curaçao criteria or molecular diagnosis based on genetic analysis of the ENG, ACVRL1, SMAD4 and GDF2 genes. In most cases, multidisciplinary management allows patients to have normal life expectancy. Advances in interventional radiology and better understanding of the pathophysiology of angiogenesis have resulted in improved therapeutic management. Anti-angiogenic treatments, such as bevacizumab (BVZ, an anti-VEGF antibody), have proven to be effective in cases involving bleeding complications and severe liver damage with cardiac repercussions. Other anti-angiogenic agents are currently being investigated, including tyrosine kinase inhibitors.

Imaging Manifestations and Interventional Treatments for Hereditary Hemorrhagic Telangiectasia

Hemorrhagic hereditary telangiectasia (HHT) is a rare autosomal dominant disorder that causes multisystem vascular malformations including mucocutaneous telangiectasias and arteriovenous malformations (AVMs). Clinical and genetic screening of patients with signs, symptoms, or a family history suggestive of HHT is recommended to confirm the diagnosis on the basis of the Curaçao criteria and prevent associated complications. Patients with HHT frequently have epistaxis and gastrointestinal bleeding from telangiectasias. Pulmonary AVMs are common right-to-left shunts between pulmonary arteries and veins that can result in dyspnea and exercise intolerance, heart failure, migraine headaches, stroke or transient ischemic attacks, brain abscesses, or in rare cases, pulmonary hemorrhage. Primary neurologic complications from cerebral AVMs, which can take on many forms, are less common but particularly severe complications of HHT. Multimodality imaging, including transthoracic echocardiography, Doppler US, CT, and MRI, is used in the screening and initial characterization of vascular lesions in patients with HHT. Diagnostic angiography is an important tool in characterization of and interventional treatments for HHT, particularly those in the lungs and central nervous system. A multidisciplinary approach to early diagnosis, treatment, imaging, and surveillance at high-volume HHT Centers of Excellence is recommended. Although a variety of idiopathic, traumatic, or genetic conditions can result in similar clinical and imaging features, the Curaçao criteria are particularly useful for the proper diagnosis of HHT. Imaging and treatment options are reviewed, with a focus on screening, diagnosis, and posttreatment findings, with the use of updated international guidelines. Online supplemental material is available for this article. ^©RSNA, 2021.

Pulmonary Vascular Complications in Hereditary Hemorrhagic Telangiectasia and the Underlying Pathophysiology

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

High output cardiac failure in 3 patients with hereditary hemorrhagic telangiectasia and hepatic vascular malformations, evaluation of treatment

BACKGROUND

This report addresses how patients with hereditary hemorrhagic telangiectasia (HHT) and high output cardiac failure (HOCF) due to hepatic vascular malformations, should be evaluated and could be treated. HHT is a genetic disorder, leading to vascular abnormalities with potentially serious clinical implications. In the liver, arteriovenous malformations occur in more than 70% of patients, but only about 8% present clinical symptoms such as HOCF with pulmonary hypertension and less commonly portal hypertension, biliary ischemia and hepatic encephalopathy.

RESULTS

Three female patients with HHT type 2 and HOCF caused by severe arteriovenous malformations in the liver are presented in this case series. The patients were seen at the HHT-Centre at Odense University Hospital. Treatment with either orthotopic liver transplantation (one patient) or bevacizumab (two patients) was initiated. All patients experienced marked symptom relief and objective improvement. New York Heart Association-class were improved, ascites, peripheral edema and hence diuretic treatment was markedly reduced or discontinued in all three patients. Bevacizumab also resulted in notable effects on epistaxis and anemia.

CONCLUSION

Our findings substantiate the importance of identification of symptomatic arteriovenous malformations in the liver in patients with HHT. Bevacizumab may possibly, as suggested in this case series and supported by previous case studies, postpone the time to orthotopic liver transplantation or even make it unnecessary. Bevacizumab represents a promising new treatment option, which should be investigated further in clinical trials.

European Reference Network for Rare Vascular Diseases (VASCERN) position statement on cerebral screening in adults and children with hereditary haemorrhagic telangiectasia (HHT)

Hereditary haemorrhagic telangiectasia (HHT) is a multisystemic vascular dysplasia inherited as an autosomal dominant trait. Approximately 10 % of patients have cerebral vascular malformations, a proportion being cerebral arteriovenous malformations (AVMs) and fistulae that may lead to potentially devastating consequences in case of rupture. On the other hand, detection and treatment related-risks are not negligible, and immediate. While successful treatment can be undertaken in individual cases, current data do not support the treatment of unruptured AVMs, which also present a low risk of bleeding in HHT patients. Screening for these AVMs is therefore controversial.

Structured discussions, distinctions of different cerebrovascular abnormalities commonly grouped into an “AVM” bracket, and clear guidance by neurosurgical and neurointerventional radiology colleagues enabled the European Reference Network for Rare Vascular Disorders (VASCERN-HHT) to develop the following agreed Position Statement on cerebral screening:

1) First, we emphasise that neurological symptoms suggestive of cerebral AVMs in HHT patients should be investigated as in general neurological and emergency care practice. Similarly, if an AVM is found accidentally, management approaches should rely on expert discussions on a case-by-case basis and individual risk-benefit evaluation of all therapeutic possibilities for a specific lesion.

2) The current evidence base does not favour the treatment of unruptured cerebral AVMs, and therefore cannot be used to support widespread screening of asymptomatic HHT patients.

3) Individual situations encompass a wide range of personal, cultural and clinical states. In order to enable informed patient choice, and avoid conflicting advice, particularly arising from non-neurovascular interpretations of the evidence base, we suggest that all HHT patients should have the opportunity to discuss knowingly brain screening issues with their healthcare provider.

4) Any screening discussions in asymptomatic individuals should be preceded by informed pre-test review of the latest evidence regarding preventative and therapeutic efficacies of any interventions. The possibility of harm due to detection of, or intervention on, a vascular malformation that would not have necessarily caused any consequence in later life should be stated explicitly.

We consider this nuanced Position Statement provides a helpful, evidence-based framework for informed discussions between healthcare providers and patients in an emotionally charged area.

Postembolotherapy Pulmonary Arteriovenous Malformation Follow-Up: A Role for Graded Transthoracic Contrast Echocardiography Prior to High-Resolution Chest CT Scan

BACKGROUND

High-resolution chest CT (HRCT) scan is recommended after pulmonary arteriovenous malformation (PAVM) embolotherapy to assess for PAVM persistence and untreated PAVM growth. Graded transthoracic contrast echocardiography (TTCE) predicts the need for embolotherapy in PAVM screening. This study sought to determine whether postembolotherapy graded TTCE can similarly predict the need for repeat embolotherapy.

METHODS

Thirty-two patients (8 men and 24 women; mean age, 51.1 ± 12.6 years) with prior PAVM embolotherapy and follow-up HRCT scan were prospectively enrolled. Patients underwent graded TTCE using a validated three-point quantitative grading scale. TTCE grade and HRCT findings were compared.

RESULTS

Median time between most recent HRCT scan and TTCE was 7 days (interquartile range, 0-272 days). Thirty patients (94%) had no PAVMs requiring repeat embolotherapy on HRCT scan. Two patients (6%) had PAVMs requiring repeat embolotherapy (feeding artery [FA] ≥ 3 mm), one with untreated PAVM growth and one with treated PAVM persistence. TTCE was positive in 88% of patients (n = 28). All patients (n = 4, 12%) with negative TTCE had no visible PAVMs on HRCT scan. Nine patients (32%) had grade 1 shunt, 10 (35%) had grade 2 shunt, and nine (32%) had grade 3 shunt. No patients with grade 1 shunt had PAVMs amenable to repeat embolotherapy on HRCT scan. All patients (n = 2) with PAVMs requiring repeat embolotherapy (FA ≥ 3 mm) had grade 3 shunt. TTCE grade was significantly associated with PAVM FA diameter (P < .001).

CONCLUSIONS

Postembolotherapy graded TTCE can predict the need for repeat embolotherapy on HRCT scan. Patients with negative TTCE and grade 1 shunt may not require HRCT follow-up and can potentially be followed with serial graded TTCE.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT02936349; URL: www.clinicaltrials.gov.

Pulmonary arteriovenous malformations in children with hereditary hemorrhagic telangiectasia: a longitudinal study

Pulmonary arteriovenous malformations (PAVMs) often occur in children with hereditary hemorrhagic telangiectasia (HHT). A 14-year longitudinal study of PAVMs in children with HHT was undertaken to assess the prevalence, the clinical impact, and progression of these malformations. This was a retrospective, single-center study from May 2002 to December 2016 of 129 children with HHT diagnosed using Curacao criteria and/or confirmed by genetic testing. Transthoracic contrast echocardiography (TTCE) was the primary screening modality in all patients and PAVMs were diagnosed based on Barzilai criteria. Moderately positive TTCE (Barzilai criteria ≥ 2) was confirmed with subsequent contrast chest CT. New PAVMs were diagnosed with a positive TTCE after an initial negative TTCE. Embolization of PAVMs were performed according to HHT consensus guidelines. Of 129 children with HHT, 76 (59%) were found to have PAVMs. Sixty-seven (88%) were positive for PAVMs on initial screening. Of 63 children without PAVMs on initial screening, 31 were followed for >1 year. Nine of the 31 (29%) developed new PAVMs after initial negative study. Thirty-eight (50%) of the total 76 children with PAVMs had or developed lesions large enough to be treated with embolization. Nine patients with PAVMs initially too small to be treated with embolization, developed progression of disease and ultimately were treated with embolization over time. The majority, 60% (23/38), of the children with large PAVMs had no related clinical symptoms. After embolization, 21% (8/38), of patients underwent repeat interventions. Genetic diagnosis, age, and gender were not associated with risk of having PAVM nor with need for repeat interventions. Nearly 60% of children with HHT develop PAVMs. The risk for new PAVMs to develop, small PAVMs to become large, and previously embolized PAVMs to require further intervention remains throughout childhood. Thus, children with HHT require continued follow-up until adulthood.

Pulmonary arteriovenous malformations: diagnosis

Pulmonary arteriovenous malformations (PAVMs) are rare, abnormal low resistance vascular structures that connect a pulmonary artery to a pulmonary vein, thereby bypassing the normal pulmonary capillary bed and resulting in an intrapulmonary right-to-left shunt. The spectrum of PAVMs extends from microscopic lesions causing profound hypoxemia and ground glass appearance on computed tomography (CT) but with normal catheter angiographic findings to classic pulmonary aneurysmal connections that abnormally connect pulmonary veins and arteries. These malformations most commonly are seen in hereditary hemorrhagic telangiectasia (HHT). They are rarely due to secondary conditions such as post congenital heart disease surgery or hepatopulmonary syndrome (HPS). The main complications of PAVM result from intrapulmonary shunt and include stroke, brain abscess, and hypoxemia. Local pulmonary complications include PAVM rupture leading to life-threatening hemoptysis or hemothorax. The preferred screening test for PAVM is transthoracic contrast echocardiography (TTCE). CT has become the gold standard imaging test to establish the presence of PAVM. Endovascular occlusion of the feeding artery is the treatment of choice. Collateralization and recanalization of PAVM following treatment may occur, and hence long term clinical and imaging follow-up is required to assess PAVM enlargement and PAVM reperfusion.

Reproducibility of right-to-left shunt quantification using transthoracic contrast echocardiography in hereditary haemorrhagic telangiectasia

Aim

Transthoracic contrast echocardiography (TTCE) is recommended for screening of pulmonary arteriovenous malformations (PAVMs) in hereditary haemorrhagic telangiectasia. Shunt quantification is used to find treatable PAVMs. So far, there has been no study investigating the reproducibility of this diagnostic test. Therefore, this study aimed to describe inter-observer and inter-injection variability of TTCE.

Methods

We conducted a prospective single centre study. We included all consecutive persons screened for presence of PAVMs in association with hereditary haemorrhagic telangiectasia in 2015. The videos of two contrast injections per patient were divided and reviewed by two cardiologists blinded for patient data. Pulmonary right-to-left shunts were graded using a three-grade scale. Inter-observer and inter-injection agreement was calculated with κ statistics for the presence and grade of pulmonary right-to-left shunts.

Results

We included 107 persons (accounting for 214 injections) (49.5% male, mean age 45.0 ± 16.6 years). A pulmonary right-to-left shunt was present in 136 (63.6%) and 131 (61.2%) injections for observer 1 and 2, respectively. Inter-injection agreement for the presence of pulmonary right-to-left shunts was 0.96 (95% confidence interval (CI) 0.9–1.0) and 0.98 (95% CI 0.94–1.00) for observer 1 and 2, respectively. Inter-injection agreement for pulmonary right-to-left shunt grade was 0.96 (95% CI 0.93–0.99) and 0.95 (95% CI 0.92–0.98) respectively. There was disagreement in right-to-left shunt grade between the contrast injections in 11 patients (10.3%). Inter-observer variability for presence and grade of the pulmonary right-to-left shunt was 0.95 (95% CI 0.91–0.99) and 0.97 (95% CI 0.95–0.99) respectively.

Conclusion

TTCE has an excellent inter-injection and inter-observer agreement for both the presence and grade of pulmonary right-to-left shunts.

Electronic supplementary material

The online version of this article (10.1007/s12471-018-1094-4) contains supplementary material, which is available to authorized users.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

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.

Life expextancy of parents with Hereditary Haemorrhagic Telangiectasia

Background

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

Method

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

Results

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

Conclusion

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

Pulmonary vascular complications of hereditary haemorrhagic telangiectasia

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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

A large pulmonary arteriovenous malformation causing cerebrovascular accidents

The incidence of pulmonary arteriovenous malformations (PAVMs) is 2.5 in 100,000. 80% are associated with Osler-Weber-Rendu syndrome or hereditary haemorrhagic telangiectasia. We report the case of a 70-year-old man with a 6 cm spherical mass incidentally found on chest X-ray. There was a localised systolic bruit over the right lower zone posteriorly; however, he was asymptomatic. He had suffered a stroke, affecting his right hand and his speech, from which he recovered. He experienced regular transient ischaemic attacks, on an average of every 2 months. He underwent a right lower lobectomy and on ligating the right lower lobe pulmonary artery the saturations of oxygen rose from 92% to 97%, demonstrating a significant right to left extracardiac shunt. Postoperative recovery was excellent and 1 year later the patient reports no further neurological symptoms. 40% of such lesions exhibit symptoms, however, only one-third are neurological. Treatment should be by percutaneous embolisation.

Clinical implications of pulmonary shunting on saline contrast echocardiography

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

Severity score for hereditary hemorrhagic telangiectasia

Background

A disease severity score in hereditary hemorrhagic telangiectasia (HHT) would be a useful tool for assessing burden of disease and for designing clinical trials. Here, we propose the first known HHT severity score, the HHT-score.

Methods

Demographics and disease characteristics were collected for the first 525 HHT patients recruited to the HHT Project of the Brain Vascular Malformation Consortium (BVMC). HHT-score was calculated based on presence of: organ arteriovenous malformations (maximum 3 points); chronic bleeding (maximum 2 points); and severe organ involvement (maximum 2 points). Points were summed and patients categorized as having mild (0–2), moderate (3–4) or severe (5–7) disease. The occurrence of “any adverse outcome” was evaluated for association with HHT-score categories.

Results

The frequency of “any adverse outcome” was significantly different across the three groups (49.6% in mild, 65.8% in moderate and 89.5% in severe, p < 0.001). Adjusting for age and gender, the risk of “any adverse outcome” was higher in the moderate (OR = 1.84, 95% CI: 1.15-2.95, p = 0.011) and severe groups (OR = 9.16, 95% CI: 1.99-42.09, p = 0.004) compared to the mild.

Conclusions

We have taken the first steps toward creating a global measure of disease severity in HHT. While the initial results are promising, further validation of the HHT-score is still required.

Optimal management of hereditary hemorrhagic telangiectasia

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