Genetic testing is available for families who are affected by HHT. Development of clinical genetic testing for HHT was a long-standing priority of the HHT Foundation and we are grateful for the efforts of the many people who have made this possible.
Genetic testing for HHT consists of analyzing DNA (the genetic material carried in cells) of the HHT-associated genes in a laboratory. Genetic testing is usually done on a small sample of blood, but can be done on a sample of saliva in certain cases. In a given family, genetic testing should start with someone who clearly has HHT.
Three different kinds of genetic tests for HHT are available.
- Sequencing of the genes involves looking at the precise sequence of building blocks in the sample of DNA to see if there is any abnormality.
- Targeted Sequencing looks to see if one particular mutation that was previously identified in another family member is present or absent.
- Deletion and Duplication testing looks to see if there is a piece of the gene that is missing or duplicated.
For a person who meets clinical diagnostic criteria for HHT, genetic testing by sequencing and deletion and duplication testing of ENG (HHT1) and ACVRL1 (HHT2) will detect a mutation in approximately 87% of those tested. If testing of ENG and ACVRL1 is negative, sequencing of SMAD4 identifies a mutation in an additional 2% of people diagnosed with HHT. For about 10-15% of people with HHT, the laboratory will not find a mutation in one of the known HHT genes.