Case Example

Annie, Tom, and Mary discuss HHT in detail, including inheritance, disease characteristics, and testing.  Annie explains that clinical testing is available for two genes associated with HHT.  She also explains that it makes the most sense to test Tom first, then, depending on the results of the test, they may be able to test other at risk individuals in the family.  However, testing these two genes will only detect a mutation in 60-80% of individuals with a clinical diagnosis of HHT.  Therefore, not finding a change in either the ENG or ALK1 genes does not change Tom’s clinical diagnosis of HHT and he will still need to be monitored for medical issues associated with HHT regardless of the test results.  In addition, Mary’s children are only at risk to have HHT if she has the condition.  Given her health status, it is unlikely, though not impossible, that she has HHT.  However once Tom gets tested, and if a mutation is detected, she can then receive testing to see if she and her children are at risk.

Why does it make the most sense to test Tom first?
Why might testing not detect a mutation in 100% of individuals with HHT?

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