Visceral manifestations in hereditary haemorrhagic telangiectasia type 2

Telangiectasia hemorrágica hereditária: ácido tranexâmico no tratamento de úlcera plantar

Relato de um caso de úlcera plantar por fístula arteriovenosa em paciente portador de telangiectasia hemorrágica hereditária ou doença de Rendu-Osler-Weber tratado com ácido tranexâmico. Este fármaco é utilizado para tratamento de epistaxe, referindo-se o principal achado deste artigo ao uso eficaz desse medicamento na terapia de úlceras plantares hemorrágicas. São descritos os aspectos fisiopatológicos e clínicos da doença e as propriedades antifibrinolíticas do ácido tranexâmico. Este foi bem tolerado e apresentou evidências de eficácia na utilização para controle do sangramento e cicatrização da úlcera.

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

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

Clinical symptoms according to genotype amongst patients with hereditary haemorrhagic telangiectasia

BACKGROUND

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

OBJECTIVE

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

DESIGN

Prospective clinical examination with genetic evaluation and follow-up.

SETTING

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

METHODS

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

RESULTS

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

CONCLUSION

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

Genotype-phenotype relationship in hereditary haemorrhagic telangiectasia

Hereditary haemorrhagic telangiectasia (HHT) is an autosomal dominant disorder characterised by vascular malformations in multiple organ systems, resulting in mucocutaneous telangiectases and arteriovenous malformations predominantly in the lungs (pulmonary arteriovenous malformation; PAVM), brain (cerebral arteriovenous malformation; CAVM), and liver (hepatic arteriovenous malformation; HAVM). Mutations in the ENG and ALK-1 genes lead to HHT1 and HHT2 respectively. In this study, a genotype-phenotype analysis was performed. A uniform and well classified large group of HHT patients and their family members were screened for HHT manifestations. Groups of patients with a clinically confirmed diagnosis and/or genetically established diagnosis (HHT1 or HHT2) were compared. The frequency of PAVM, CAVM, HAVM, and gastrointestinal telangiectases were determined to establish the genotype-phenotype relationship. The analysis revealed differences between HHT1 and HHT2 and within HHT1 and HHT2 between men and women. PAVMs and CAVMs occur more often in HHT1, whereas HAVMs are more frequent in HHT2. Furthermore, there is a higher prevalence of PAVM in women compared with men in HHT1. In HHT1 and HHT2, there is a higher frequency of HAVM in women. HHT1 has a distinct, more severe phenotype than HHT2. There is a difference in the presence of symptoms between men and women. With these data, genetic counselling can be given more accurately when the family mutation is known.

ALK-1 mutations in liver transplanted patients with hereditary hemorrhagic telangiectasia

Hereditary haemorrhagic telangiectasia (HHT) is an autosomal dominantly inherited disorder characterized by cutaneous and mucosal telangiectasias, epistaxis and arteriovenous malformations in lung, liver, central nervous system, and gastrointestinal tract. Mutations in the genes for endoglin (ENG) and for activin A receptor type II-like kinase 1 (ALK-1) have been identified to be associated with HHT. Intrahepatic manifestation in HHT might lead to the requirement of liver transplantation. We report here on 6 liver transplanted patients and 2 who were scheduled for liver transplantation due to intrahepatic HHT, in whom both genes were sequenced. Mutation analysis revealed in all patients the presence of mutations in ALK-1. In conclusion, these results are of possible prognostic value concerning the need of liver transplantation in HHT patients.

Liver transplantation for cardiac failure in patients with hereditary hemorrhagic telangiectasia

Liver involvement in hereditary hemorrhagic telangiectasia may lead to high-output cardiac failure. Few data have been reported on orthotopic liver transplantation (OLT) for these patients. In this paper, we describe two patients treated by OLT as a salvage procedure for cardiac failure, and we review literature on this subject. Our two patients resumed normal cardiac function after OLT. This procedure appears to be a promising therapy with good long-term results despite dissection difficulties encountered due to the collateral arterial network reorganization.

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

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

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

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

Mutation Analysis in Spanish Patients with Hereditary Hemorrhagic Telangiectasia: Deficient Endoglin Up-regulation in Activated Monocytes

Background: Mutations in the endoglin (ENG) or ALK1 genes are responsible for hereditary hemorrhagic telangiectasia types 1 and 2 (HHT1 and HHT2), respectively, a dominant vascular dysplasia caused by haploinsufficiency. No formal mutation studies of patients with HHT have been conducted in Spain.

Methods: ENG and ALK1 mutation analyses were carried out in 13 Spanish HHT patients diagnosed according to the Curaçao criteria. Because endoglin is up-regulated at the cell surface during the monocyte-macrophage transition, endoglin concentrations in activated monocytes were determined by immunofluorescence flow cytometry in a systematic analysis. As controls, 40 non-HHT volunteers were studied for up-regulation of endoglin in activated monocytes.

Results: The mutation responsible for HHT was identified in eight patients belonging to two unrelated families. One of the families has a nonsense mutation in exon 4 (c.511C>T; R171X) of the ENG gene, and accordingly the disorder was identified as HHT1. The other family has a missense mutation affecting exon 8 (c.1120C>T; R374W) of the ALK1 gene, and hence is a HHT2 family. Interestingly, endoglin up-regulation was deficient in activated monocytes of both HHT1 and HHT2 patients compared with controls. By contrast, endoglin up-regulation was age-independent in control donors across a broad range of ages. The extent of endoglin up-regulation in activated monocytes was most diminished in those patients with the most severe symptoms.

Conclusions: Endoglin up-regulation in activated monocytes is impaired in HHT1 and HHT2 patients and is age-dependent in both HHT types. Endoglin expression may predict the clinical severity of HHT.

The biological "scrabble" of pulmonary arteriovenous malformations: considerations in the setting of cavopulmonary surgery

Pulmonary arteriovenous fistulas are vascular malformations, which, by virtue of producing abnormal vascular connections proximal to the units of gas exchange, result in intrapulmonary right-to-left shunting. These malformations or fistulas reflect at least in part disordered angiogenesis, and less commonly recruitment and dilation of pre-existing vascular channels. Pulmonary arteriovenous fistulas occur in a number of diverse clinical settings. Such fistulas are a well-established feature of the Weber-Osler-Rendu complex, or hereditary haemorrhagic telangiectasia, an autosomal dominant vascular dysplasia characterized by mucocutaneous telangiectasis, epistaxis, gastrointestinal haemorrhage, and arteriovenous malformations in the lung, brain, liver and elsewhere. They are also seen in the patient with acute or chronic liver disease, disease that is usually but not invariably severe, or those with non-cirrhotic portal hypertension. They may occur as congenital malformations, single or diffuse, large or small in isolation, and when large or extensive enough may result in hypoxaemia, clinical cyanosis, and heart failure. Cerebral vascular accidents are also a well-known complication of this disorder. An extensive literature has accumulated with regard to the pulmonary arteriovenous fistulas seen in the setting of the Weber-Osler-Rendu complex, and there is considerable information on the genetics, basic biology, clinical findings, complications and therapeutic interventions of these malformations in the setting of this syndrome. These issues, however, are not the primary considerations of this review, although some aspects of this fascinating disorder will be discussed later. Rather the focus will be on pulmonary arteriovenous malformations that develop in the setting of cavopulmonary surgery, and their relationship to the pulmonary arteriovenous fistulas occurring in the hepatopulmonary syndrome. The complex tapestry of these overlapping and intersecting clinical observations will be unfolded in the light of their chronology.

Molecular and functional analysis identifies ALK-1 as the predominant cause of pulmonary hypertension related to hereditary haemorrhagic telangiectasia

BACKGROUND

Mutations of the transforming growth factor beta (TGFbeta) receptor components ENDOGLIN and ALK-1 cause the autosomal dominant vascular disorder hereditary haemorrhagic telangiectasia (HHT). Heterozygous mutations of the type II receptor BMPR2 underlie familial primary pulmonary hypertension.

OBJECTIVE

To investigate kindreds presenting with both pulmonary hypertension and HHT.

METHODS

Probands and families were identified by specialist pulmonary hypertension centres in five countries. DNA sequence analysis of ALK-1, ENDOGLIN, and BMPR2 was undertaken. Cellular localisation was investigated by heterologous overexpression of mutant constructs in both BAEC and HeLa cells. The impact of a novel sequence variant was assessed through comparative analysis and computer modelling.

RESULTS

Molecular analysis of 11 probands identified eight missense mutations of ALK-1, one of which was observed in two families. Mutations were located within exons 5 to 10 of the ALK-1 gene. The majority of ALK-1 mutant constructs appeared to be retained within the cell cytoplasm, in the endoplasmic reticulum. A novel GS domain mutation, when overexpressed, reached the cell surface but is predicted to disrupt conformational changes owing to loss of a critical hydrogen bond. Two novel missense mutations were identified in ENDOGLIN.

CONCLUSIONS

The association of pulmonary arterial hypertension and HHT identifies an important disease complication and appears most common among subjects with defects in ALK-1 receptor signalling. Future studies should focus on detailed molecular analysis of the common cellular pathways disrupted by mutations of ALK-1 and BMPR2 that cause inherited pulmonary vascular disease.