HHT Genetic Testing

Making the diagnosis of HHT in a patient allows for the appropriate screening and preventative treatment to be undertaken in the patient and their affected family members. HHT has traditionally been diagnosed on the basis of its clinical features but can now also be diagnosed using genetic testing.

Genetic testing can be used to confirm a diagnosis and identify family members at risk, allowing screening for AVMs. In addition, there is evidence that the type of mutation a person has can predict the likelihood of developing AVMs in particular locations. Genetic testing in children can be valuable, as it can direct these screening methods, leading to early detection and treatment of potentially life-threatening AVMs.

Genes Tested

  • ENG (endoglin). Hereditary hemorrhagic telangiectasia type 1 (HHT1)
  • ACVRL1 (ALK1). Hereditary hemorrhagic telangiectasia type 2 (HHT2).
  • SMAD4 (MADH4). Some patients with JP-HHT may show only symptoms of HHT with occult manifestation of juvenile polyposis (JP). The mutations leading to JP-HHT are most often found in the COOH-terminus of SMAD4.

Screening Key Points

  • The most serious complications of HHT are invisible, but can be prevented through early diagnosis and treatment
  • Someone in the family with symptoms of HHT should be tested first to identify the family’s genetic mutation
  • If a familial mutation is found, then genetic testing of relatives can determine who does and does not have HHT
  • Testing of young at-risk children will spare 50% from evaluations and imaging and its radiation while identifying children who need screening and management
  • Genetic testing can be done on a sample of blood or saliva and ordered through primary care doctors, HHT Centers of Excellence, or local genetics clinics
  • Genetic testing is usually covered by insurance
  • Legal protections prohibit genetic discrimination in health insurance and employment, but not life insurance.

CT & MRI Scans

Computerized tomography (CT) and magnetic resonance imaging (MRI) scans take pictures of the brain tissues and arteries. CT scans are usually better at revealing any cranial bleeding that may already be present. A spinal tap, where a doctor draws fluid from the spine, can check for signs of bleeding in the brain. Cerebral angiograms can also check for bleeding and any abnormalities in the brain arteries.