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Table 1 Key features of C9ORF72 genetic counseling

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.
  1. ALS, amyotrophic lateral sclerosis; C9ORF72, chromosome 9 open reading frame 72; FTD, frontotemporal degeneration.