The Comprehensive HHT Outcomes Registry of the United States (CHORUS) is an observational registry of patients diagnosed with Hereditary Hemorrhagic Telangiectasia (HHT). The purpose of this study is to better understand HHT, the symptoms and complications it causes, and the impact the disease has on people's lives. The investigators will collect long-term information about the participant, allowing us to understand how the disease changes over time, and what factors can influence those changes. Ultimately, this should help improve treatments for the disease.

Another important goal of the study is to provide a way to contact people to participate in future clinical trials and other research. The registry will be a centralized resource for recruitment for clinical trials. People in the registry will not be obligated to join any of these additional studies, but if interested, can agree to be contacted if they may be eligible for a study.

Participants will:

• Be asked to provide permission to collect information from their medical records, including things like demographic information, diagnosis information, family history, test results, treatment information, symptoms, complications, lifestyle and other relevant medical information.
• Be asked study-related questions by phone or at a clinic visit.
• Be asked study-related questions every year after enrollment for up to 10 years or until the study ends. A member of the study team will communicate with participants by phone or at clinic visits to collect information regarding any changes to their health over the previous year/s including new test results, treatment information, symptoms, and complications from HHT.

The Comprehensive HHT Outcomes Registry of the United States (CHORUS) is a research initiative led by the HHT Foundation International, Inc. ("Cure HHT"). The study focuses on Hereditary Hemorrhagic Telangiectasia (HHT), a rare genetic disorder characterized by the development of abnormal blood vessels in various organs of the body, including the brain, spine, lungs, liver, GI tract, skin, nasal mucosa, and oral cavity. The prevalence of HHT is estimated to be 1 in 5000, affecting children and adults. These abnormal blood vessels can lead to acute and chronic bleeding, stroke, heart failure, and death. Treatments are currently predominately limited to managing complications, while approximately 90% of adults have ongoing symptoms, despite the best surgical and medical therapies. With recent drug developments related to angiogenesis, there is hope for effective novel therapies.

A natural history registry for HHT has significant implications for improving the understanding and management of this rare genetic disorder. The purpose of this study is to better understand HHT, the symptoms and complications it causes ("outcomes"), and to understand how the disease impacts people's lives. The investigators hypothesize that a natural history registry for HHT will improve our understanding of the disease, lead to better management of patients, and ultimately, contribute to developing novel therapies to treat this disease.

The investigators will collaborate with multiple HHT Centers of Excellence across the U.S. to establish a comprehensive registry of HHT patients. The study aims to enroll approximately 10,000 HHT patients over a 10-year period. Longitudinal data will be collected both retrospectively and prospectively, with a focus on increasing the understanding of this rare disease, accelerating the development of new diagnostic and treatment options, and working collaboratively with clinicians who care for individuals with HHT to identify and address gaps in the system of care, especially those from underserved populations.

The study aims to serve as a centralized resource for future clinical trials and research in HHT. Data security and confidentiality are prioritized, and participants have the option to withdraw from the study at any time. The study is funded by the U.S. Department of Health Resources and Service Administration (HRSA) through a grant awarded to Cure HHT.

Inclusion Criteria:

• Diagnosed with HHT based on the Curacao diagnostic criteria or genetic testing.
• Able to provide informed consent or informed consent via a parent or legally authorized representative due to their age or medical condition.

Exclusion Criteria:

• Unable to provide informed consent or informed consent via a parent or legally authorized representative.

All patients evaluated and diagnosed with HHT in the U.S. will be eligible to participate in the study.