From the Guidelines
Hereditary hemorrhagic telangiectasia (HHT) is estimated to affect approximately 1 in 5000 people worldwide, as indicated by the most recent and highest quality study 1. This condition is characterized by the presence of vascular malformations, which can lead to chronic bleeding, acute hemorrhage, and complications from shunting through these malformations. The estimated prevalence of HHT may vary by region, but the study published in the Annals of Internal Medicine provides the most up-to-date and reliable estimate 1. Some key points to consider about HHT include:
- It is an autosomal dominant disease, meaning a child has a 50% chance of inheriting it if one parent has the disorder.
- The condition is often underdiagnosed due to varying severity of symptoms, even within families.
- Patients may experience mild symptoms that do not prompt medical attention, while others may have more severe manifestations like recurrent nosebleeds, gastrointestinal bleeding, or complications from malformations in the lungs, liver, or brain. The Second International HHT Guidelines process aimed to develop evidence-based consensus guidelines for the management and prevention of HHT-related symptoms and complications, and the resulting recommendations should facilitate implementation of key components of HHT care into clinical practice 1.
From the Research
Prevalence of Hereditary Hemorrhagic Telangiectasia
- Hereditary hemorrhagic telangiectasia (HHT) is a rare autosomal dominant disorder, affecting up to 1 in 5,000 individuals 2.
- The disorder is characterized by vascular dysplasia, including systemic telangiectases and arteriovenous malformations (AVMs) 3, 2, 4.
- HHT is caused by loss-of-function mutations in the BMP9-10/ENG/ALK1/SMAD4 signaling pathway, an important mediator of vascular quiescence 2.
Clinical Features and Diagnosis
- The clinical manifestations of HHT are variable, and patients often experience delays in diagnosis and treatment 3.
- The most common presentations of HHT include epistaxis, telangiectases of the oral buccal mucosa, tongue and/or lips, pulmonary AVMs, hepatic AVMs, gastrointestinal telangiectases, and encephalic AVMs 3.
- Diagnosis can be made using the Curaçao criteria or by identifying the affected gene 4.
- Molecular analysis has identified mutations in the ENG and ACVRL1 genes in up to 85% of HHT cases, with additional genes such as SMAD4 and GDF2 also implicated in a smaller number of patients 5.
Epidemiology and Genetics
- HHT is an inherited disease with a significant impact on affected individuals, with complications ranging from mild to life-threatening events 2, 4.
- The disorder is underdiagnosed, and DNA testing has recently become available to facilitate presymptomatic screening and prevent catastrophic complications 6.
- The prevalence of HHT is estimated to be around 1 in 5,000 individuals, although the exact prevalence may vary depending on the population being studied 2.