From: Genetic counseling for FTD/ALS caused by the C9ORF72 hexanucleotide expansion
Feature | Salient characteristics |
---|---|
Family history assessment | A three-generation pedigree should document FTD, ALS, other dementia, Parkinsonism, psychiatric disease. |
 | Medical records, autopsy studies may clarify diagnoses. |
 | Incomplete information, misdiagnoses, early death, false paternity, undisclosed adoption may complicate family history. |
 | An autosomal dominant pattern is most suggestive of the expansion, but a mutation cannot be ruled out completely in sporadic cases. |
Discussion of risks, benefits, and limitations of C9ORF72 genetic testing | Diagnostic testing should be considered in both sporadic and familial cases. Predictive genetic testing should be given careful consideration. |
 | Presence of the expansion cannot predict age of onset or symptom expressivity. |
 | Limited information is known about anticipation, penetrance, and intermediate alleles. |
 | Predictive genetic testing should be offered via a modified Huntington disease protocol, which includes pre-test and post-test genetic counseling; neurologic and cognitive assessment; psychological evaluation; and in-person disclosure with a support person. |
 | Some families with an autosomal dominant history of FTD and/or ALS will have no identifiable expansion. Another genetic etiology is likely. Family members remain at risk. DNA banking is a viable option for such families. |
 | DNA banking is a viable option for families who are not ready for clinical diagnostic testing. |
Anticipatory guidance for at-risk families | Communication about family members' motivation to seek genetic testing may identify concerns or expectations for clinicians to address. |
 | Communication about the psychological burden of disease and impact of caregiving may help clinicians identify family members' need for support or other resources. |
 | Pre-test communication about the psychosocial impact of genetic testing may help families prepare for possible outcomes and/or uncertainty. |
 | Pre-test communication about genetic privacy and discrimination concerns may help families make future care or financial plans. |