When there is a family history of a genetic disorder, is it necessary to test an affected family member before testing presymptomatic family members?
Ideally, an affected family member should be tested first in order to confirm the diagnosis and the type of mutation. In the absence of this information, the significance of a negative test result is reduced. The importance of identifying a mutation in an affected individual prior to presymptomatic testing in other family members is illustrated in the case of Early Onset Familial Alzheimer’s Disease (EOFAD). At least three genes are known to be associated with EOFAD. Mutations in the Presenilin-1 gene are known to be associated with 50 – 60% of EOFAD cases. Without verification of a familial Presenilin-1 mutation, there are three possible explanations for a presymptomatic individual testing negative: one, the patient is negative for the familial mutation, two, the patient is negative for a mutation in an untested gene, three, the patient is positive for a mutation in an untested gene. Confirmation of a Presenilin-1 mutation in an affected family member would eliminate the latter two po
Related Questions
- When there is a family history of a genetic disorder, is it necessary to test an affected family member before testing presymptomatic family members?
- If a symptomatic patient has a negative genetic test result, does it mean the patient is not affected with the tested disorder?
- Should I inform California Cryobank if I have a family history of a particular genetic disorder?
