Is Hereditary Hemorrhagic Telangiectasia hereditary?

Hereditary Hemorrhagic Telangiectasia (HHT), also known as Osler-Weber-Rendu syndrome, is a genetic condition that is inherited in an autosomal dominant pattern. Because it is hereditary, an affected parent has a 50% chance of passing the pathogenic variant to each child, regardless of the child's biological sex.

Is Hereditary Hemorrhagic Telangiectasia hereditary or genetic?

Hereditary Hemorrhagic Telangiectasia is both a genetic and a hereditary condition. "Genetic" means it is caused by a change (mutation) in a person's DNA, while "hereditary" means this mutation can be passed down from parent to child. The condition is primarily caused by variants in the ENG (HHT1), ACVRL1 (HHT2), or SMAD4 genes. Because it follows an autosomal dominant inheritance pattern, only one copy of the mutated gene—inherited from either parent—is sufficient to cause the disease. In our DiseaseMaps community, 141 members have shared their experiences, highlighting the importance of understanding the familial nature of this disorder.

What is the risk of passing Hereditary Hemorrhagic Telangiectasia to children?

For individuals diagnosed with Hereditary Hemorrhagic Telangiectasia, the risk of passing the condition to offspring is 50% for each pregnancy. It is important to note that the clinical severity of Hereditary Hemorrhagic Telangiectasia can vary significantly, even within the same family. This phenomenon, known as variable expressivity, means that a parent may have mild symptoms while their child could potentially experience more severe manifestations, such as pulmonary arteriovenous malformations or gastrointestinal bleeding. While de novo (spontaneous) mutations do occur, they are relatively rare compared to inherited cases; the vast majority of individuals with Hereditary Hemorrhagic Telangiectasia have at least one affected parent.

How is genetic testing used for Hereditary Hemorrhagic Telangiectasia?

Genetic testing is a vital tool for confirming a clinical diagnosis of Hereditary Hemorrhagic Telangiectasia. When a specific pathogenic variant is identified in an affected family member, targeted testing can be offered to at-risk relatives. Clinical geneticists generally recommend the following approach:

• Diagnostic testing: Confirming the diagnosis in a symptomatic individual through gene sequencing.


• Cascade testing: Screening asymptomatic family members to determine if they carry the familial mutation.


• Prenatal and Preimplantation Genetic Testing (PGT): Options available for parents who wish to understand the genetic status of a pregnancy or embryos prior to implantation.


• Genetic Counseling: Essential to discuss the implications of test results, the potential for variable severity, and reproductive planning.

What role does genetic counseling play for families?

Genetic counseling is highly recommended for any family affected by Hereditary Hemorrhagic Telangiectasia. A genetic counselor helps families navigate the complexities of inheritance, explains the likelihood of transmission, and provides emotional support regarding the challenges of living with a chronic condition. Because Hereditary Hemorrhagic Telangiectasia requires lifelong monitoring of vascular malformations, counseling also helps families establish a proactive screening plan for children who test positive for the familial variant.

Next steps

• Consult with a board-certified clinical geneticist to discuss family history and potential genetic testing.


• Request a referral to a dedicated HHT Center of Excellence for specialized, multidisciplinary care.


• Connect with the 141 members of the DiseaseMaps community to share experiences and coping strategies.


• Review resources from the HHT Foundation to stay updated on current clinical trials and management guidelines.

Medical disclaimer: This information is for educational purposes only and does not constitute medical advice, diagnosis, or treatment; always seek the advice of your physician or other qualified health provider with any questions regarding a medical condition.

References

• Orphanet: Hereditary Hemorrhagic Telangiectasia (ORPHA:804)


• NIH Genetic and Rare Diseases Information Center (GARD): Hereditary Hemorrhagic Telangiectasia


• OMIM (Online Mendelian Inheritance in Man): HHT1 (#187300), HHT2 (#600376)


• Cure HHT (HHT Foundation International)