Detection of a significant association between mutations in the ACVRL1 gene and hepatic involvement in German patients with hereditary haemorrhagic telangiectasia

Computational and Experimental Analyses for Pathogenicity Prediction of ACVRL1 Missense Variants in Hereditary Hemorrhagic Telangiectasia

Hereditary hemorrhagic telangiectasia (HHT) is a vascular disease caused by the defects of ALK1/ACVRL1 receptor signaling. In this study, we evaluated 25 recently identified ACVRL1 missense variants using multiple computational pathogenicity classifiers and experimentally characterized their signal transduction capacity. Three extracellular residue variants showed no detectable cell surface expression and impairment of bone morphogenetic protein 9 (BMP9) responsiveness of SMAD-dependent transcription in luciferase assays. Four variants with amino acid replacement in the motifs essential for the intracellular kinase function lost SMAD-dependent signaling. Most of other variations in the kinase domain also caused marked downregulation of signaling; however, two variants behaved as the wild-type ACVRL1 did, while computational classifiers predicted their functional abnormalities. Three-dimensional structure prediction using the ColabFold program supported the significance of the L45 loop and NANDOR domain of ACVRL1 for its association with SMAD1 and BMPR2, respectively, and the variations in these motifs resulted in the reduction of SMAD signaling. On the other hand, two of the GS domain variants maintained high signal transduction capacity, which did not accord with their computational pathogenicity prediction. These results affirm the requirement of a combinatory approach using computational and experimental analyses to accurately predict the pathogenicity of ACVRL1 missense variants in the HHT patients.

A Rare Case of Upper Gastrointestinal Bleeding: Osler-Weber-Rendu Syndrome

Osler-Weber-Rendu disease, also known as hereditary hemorrhagic telangiectasia (HHT), is a rare, autosomal dominant condition that affects approximately 1 in 5000 patients causing abnormal blood vessel formation. HHT patients have mucocutaneous telangiectasias and arteriovenous malformations in various organs. The most prominent symptom of HHT is epistaxis, which, together with gastrointestinal bleeding, may cause iron deficiency anemia. This study is a case report of a 62-year-old patient who was admitted to the Department of Gastroenterology due to acute upper gastrointestinal bleeding and a history of recurrent epistaxis and melena for 4 days, which was confirmed in digital rectal examination. Urgent upper gastrointestinal endoscopy revealed active bleeding from multiple angioectatic spots with bright-looking salmon-colored patches in the antrum and the body suggestive of HHT. The bleeding from two angioectatic spots was stopped by argon plasma coagulation, and four clips were placed to provide good hemostasis. The patient was treated with a proton pomp inhibitor infusion and iron infusion. She was discharged with no signs of GI bleeding, normalized iron levels and a diagnosis of HHT. She was referred to further genetic testing, including evaluation of first-degree relatives. She also had performed unenhanced thin-cut computed tomography (CT) with angiography to exclude the presence of pulmonary arteriovenous malformations (PAVMs). Due to the fact that the patient did not manifest any other HHT-related symptoms and that the instrumental screening discloses no silent AVMs in other organs, the “watch-and-wait strategy” was applied. Although, Osler-Weber-Rendu syndrome is widely described in the medical literature, effective treatment of gastrointestinal telangiectasias is not always available and still lacks standardization to date, which makes the management of gastroenterological involvement still a challenging issue.

Clinical characteristics and prognosis analysis of idiopathic and hereditary pulmonary hypertension patients with ACVRL1 gene mutations

Pulmonary arterial hypertension is a kind of heart and lung vascular disease with low incidence and poor prognosis. Genetic variants are the important factors of pulmonary arterial hypertension. The mutations of activin receptor-like kinase-1 (ACVRL1) could cause pulmonary arteriole obstruction and occlusion in pulmonary arterial hypertension patients. The ACVRL1 gene mutation and clinical characteristics of Chinese idiopathic or hereditary pulmonary hypertension (IPAH/HPAH) patients are still unclear. This study aimed to retrospectively study the mutation characteristics of ACVRL1 gene in Chinese IPAH/HPAH patients and its effect on clinical prognosis. We analyzed the clinical, functional, hemodynamic and mutation characteristics of 12 IPAH/HPAH patients with ACVRL1 mutations and compared with 94 IPAH/HPAH patients (27 patients carried bone morphogenetic protein receptor type 2 (BMPR2) mutations and 67 without mutations). All ACVRL1 mutations of 12 patients were single nucleotide missense mutations. The ratio of male to female in 12 patients was 1:1. The diagnosis age of ACVRL1 mutation patients was younger than that of BMPR2 mutation patients (13.6 ± 11.3 years vs. 16.0 ± 12.9 years) but higher than that of patients without mutations (13.6 ± 11.3 years vs. 8.8 ± 8.5 years, p = 0.006). IPAH/HPAH patients with ACVRL1 mutation have rapid disease progresses, high overall mortality rate (approximately 50%) and no response to the acute pulmonary vasodilation test. In conclusion, this is the first study to analyze the ACVRL1 gene mutation and clinical characteristics of Chinese IPAH/HPAH patients. It is beneficial to screen ACVRL1 gene mutation for IPAH/HPAH patients to facilitate genetic counseling and early prevention and treatment.

Founder Effects in Hereditary Hemorrhagic Telangiectasia

A founder effect can result from the establishment of a new population by individuals from a larger population or bottleneck events. Certain alleles may be found at much higher frequencies because of genetic drift immediately after the founder event. We provide a systematic literature review of the sporadically reported founder effects in hereditary hemorrhagic telangiectasia (HHT). All publications from the ACVRL1, ENG and SMAD4 Mutation Databases and publications searched for terms “hereditary hemorrhagic telangiectasia” and “founder” in PubMed and Scopus, respectively, were extracted. Following duplicate removal, 141 publications were searched for the terms “founder” and “founding” and the etymon “ancest”. Finally, 67 publications between 1992 and 2020 were reviewed. Founder effects were graded upon shared area of ancestry/residence, shared core haplotypes, genealogy and prevalence. Twenty-six ACVRL1 and 12 ENG variants with a potential founder effect were identified. The bigger the cluster of families with a founder mutation, the more remarkable is its influence to the populational ACVRL1/ENG ratio, affecting HHT phenotype. Being aware of founder effects might simplify the diagnosis of HHT by establishing local genetic algorithms. Families sharing a common core haplotype might serve as a basis to study potential second-hits in the etiology of HHT.

Hereditary hemorrhagic telangiectasia: how to efficiently detect hepatic abnormalities using ultrasonography

INTRODUCTION

Hereditary hemorrhagic telangiectasia (HHT) is a multiorgan genetic angiodysplastic affection characterized by visceral vascular malformations. It affects mainly the brains, lungs, gastrointestinal tract, and nasal mucosa. Unlike those organs, hepatic involvement, although very frequently occurring, is insufficiently recognized, mainly because of the complex vascular structure of this organ. Thus, treating HHT patients requires a solid understanding of these hepatic anomalies. It is especially important for any general clinicians to be able to recognize clinical findings in HHT, which leads to a high suspicion of HHT and have an index of suspicion for liver abnormalities of HHT. For this purpose, keen awareness of clinical as well as hepatic sonographic (US) findings is paramount.

AIM

The aim of this review is to summarize previously reported findings on the hepatic US through a thorough analysis of related articles, and to (a) determine the role of US in the diagnosis of hepatic involvement in HHT patients and (b) propose the most simple and easy way to detect HHT-related abnormalities during routine US examinations.

CONCLUSION

Hepatic US serves to diagnose the detailed complex hepatic changes typical of HHT, and contributes to increased diagnostic confidence of hepatic changes in HHT patients, with the most simple way not to overlook HHT-related abnormalities being to find hepatic artery dilatation.

Pulmonary Hypertension and Hereditary Hemorrhagic Telangiectasia Related to an ACVRL1 Mutation

Pulmonary hypertension and hereditary hemorrhagic telangiectasia (HHT) have an association mediated by activin A receptor type II-like 1 (ACVRL1) gene pathogenic variants. A 30-year-old woman was previously admitted to a hospital due to lung hemorrhage, and was diagnosed with pulmonary hypertension, but stopped follow-up visits. At 48 years of age, she was admitted to our hospital and was diagnosed with HHT. Genetic testing revealed an ACVRL1 pathogenic variant. After the initiation of pulmonary vasodilator treatment, the patient's mean pulmonary artery pressure started to decrease from 43 mmHg, declining to 37 mmHg when she was 58 years of age. This is the first report describing the 28-year follow-up of an HHT and pulmonary hypertension patient with an ACVRL1 mutation.

Mutation in BMPR2 Promoter: A 'Second Hit' for Manifestation of Pulmonary Arterial Hypertension?

BACKGROUND

Hereditary pulmonary arterial hypertension (HPAH) can be caused by autosomal dominant inherited mutations of TGF-β genes, such as the bone morphogenetic protein receptor 2 (BMPR2) and Endoglin (ENG) gene. Additional modifier genes may play a role in disease manifestation and severity. In this study we prospectively assessed two families with known BMPR2 or ENG mutations clinically and genetically and screened for a second mutation in the BMPR2 promoter region.

METHODS

We investigated the BMPR2 promoter region by direct sequencing in two index-patients with invasively confirmed diagnosis of HPAH, carrying a mutation in the BMPR2 and ENG gene, respectively. Sixteen family members have been assessed clinically by non-invasive methods and genetically by direct sequencing.

RESULTS

In both index patients with a primary BMPR2 deletion (exon 2 and 3) and Endoglin missense variant (c.1633G>A, p.(G545S)), respectively, we detected a second mutation (c.-669G>A) in the promoter region of the BMPR2 gene. The index patients with 2 mutations/variants were clinically severely affected at early age, whereas further family members with only one mutation had no manifest HPAH.

CONCLUSION

The finding of this study supports the hypothesis that additional mutations may lead to an early and severe manifestation of HPAH. This study shows for the first time that in the regulatory region of the BMPR2 gene the promoter may be important for disease penetrance. Further studies are needed to assess the incidence and clinical relevance of mutations of the BMPR2 promoter region in a larger patient cohort.

Hemodynamic and genetic analysis in children with idiopathic, heritable, and congenital heart disease associated pulmonary arterial hypertension

Background

Aim of this prospective study was to compare clinical and genetic findings in children with idiopathic or heritable pulmonary arterial hypertension (I/HPAH) with children affected with congenital heart defects associated PAH (CHD-APAH).

Methods

Prospectively included were 40 consecutive children with invasively diagnosed I/HPAH or CHD-APAH and 117 relatives. Assessment of family members, pedigree analysis and systematic screening for mutations in TGFß genes were performed.

Results

Five mutations in the bone morphogenetic protein type II receptor (BMPR2) gene, 2 Activin A receptor type II-like kinase-1 (ACVRL1) mutations and one Endoglin (ENG) mutation were found in the 29 I/HPAH children. Two mutations in BMPR2 and one mutation in ACVRL1 and ENG, respectively, are described for the first time. In the 11 children with CHD-APAH one BMPR2 gene mutation and one Endoglin gene mutation were found. Clinical assessment of relatives revealed familial aggregation of the disease in 6 children with PAH (HPAH) and one CHD-APAH patient. Patients with mutations had a significantly lower PVR.

Conclusion

Mutations in different TGFß genes occurred in 8/29 (27.6%) I/HPAH patients and in 2/11 (18.2%) CHD-APAH patients and may influence the clinical status of the disease. Therefore, genetic analysis in children with PAH, especially in those with I/HPAH, may be of clinical relevance and shows the complexity of the genetic background.

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

BACKGROUND

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

AIM

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Molecular diagnosis in hereditary hemorrhagic telangiectasia: findings in a series tested simultaneously by sequencing and deletion/duplication analysis

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant vascular disorder characterized by a unique pattern of telangiectasia and arteriovenous malformations (AVMs). Mutations in one of two genes (ENG and ACVRL1) cause approximately 85% of cases. Genetic testing impacts clinical management because genotype/phenotype correlations exist, and early preventive screening for internal AVMs is recommended in affected individuals prior to the age at which a diagnosis can typically be made based on clinical criteria. We report 383 consecutive cases in which sequencing and large deletion/duplication analysis were performed simultaneously for endoglin (ENG) and activin-like receptor kinase 1 (ACVRL1). We report the first case of mosaicism in an affected individual and 61 novel mutations. We discuss the potential benefits of a diagnostic testing approach for HHT whereby ENG and ACVRL1 are analyzed simultaneously by sequencing and a method which detects large deletion/duplications, rather than by a sequential or reflex testing protocol. We report a case in which a deletion would probably have been missed if large deletion/duplication analysis was performed only if a suspected pathogenic mutation was not first identified by sequencing.

Vascular disorders of the liver

This guideline has been approved by the American Association for the Study of Liver Diseases (AASLD) and represents the position of the association.