Hereditary Haemorrhagic Telangiectasia Working Group (HHT-WG)

Disease Information

Hereditary Haemorrhagic Telangiectasia (HHT), often recognized as a relatively common condition within the “rare” vascular disease category, presents unique screening and management challenges. Characterized by abnormal vascular structures leading to a spectrum of complications, HHT requires a nuanced approach to symptom management, underscoring the need for advancements in targeting the disease’s pathophysiology.

In 2019, the VASCERN HHT Working Group provided a definitive description of HHT for ORPHANET, establishing a foundation for consistent diagnosis and treatment strategies (see here). Unlike other conditions within VASCERN, HHT is distinguished by chronic bleeding from abnormal vascular structures and risks associated with paradoxical emboli, particularly through pulmonary arteriovenous malformations (AVMs), and the broader implications of systemic AVMs.

The complexity of HHT manifestations often necessitates a multidisciplinary medical team. Symptoms range from nosebleeds (epistaxis) and gastrointestinal bleeding leading to iron deficiency anemia, to more severe outcomes from larger AVMs in the lungs, liver, and brain, including the potential for hemorrhage. Pulmonary AVMs notably increase the risk of ischemic strokes, cerebral abscesses, and hypoxemia, while systemic AVMs can elevate cardiac demand, further complicated by iron deficiencies and/or hypoxemia. Remarkably, with appropriate care, individuals with HHT can maintain a quality life expectancy, partly due to a reduced risk of certain cancers and heart attacks.

Diagnosis of HHT is primarily clinical, based on the Curaçao criteria (Shovlin et al., 2000), with molecular diagnostics available for identifying pathogenic variants in ACVRL1 (ALK1), ENG, and SMAD4 genes in over 90% of clinically diagnosed cases.

The estimated incidence and prevalence numbers is 500 million inhabitants within the European Union with about 6 million newborns annually.

Sub-thematic areas of expertise Rare or complex disease(s) or condition(s) or highly specialized interventions Code/ICD/ Orphacode / Group of codes Incidence (number of case / year (in the EU) Prevalence (in the EU)
HHT Hereditary Hemorrhagic Telangiectasia ICD-10: 178.0ORPHA774 1000 Estimated to be 1/6000(83000 patients)

Last updated: February 13, 2023

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