Abstract
Objective We aimed to describe the population of subjects seeking presymptomatic counseling for amyotrophic lateral sclerosis and/or frontotemporal dementia (ALS/FTD) and compared them with those demanding the well-established presymptomatic test for Huntington disease (HD).
Methods We retrospectively examined the requests of a cohort of individuals at risk of familial ALS/FTD and 1 at risk of HD over the same time frame of 11 years. The individuals were seen in the referral center of our neurogenetics unit.
Results Of the 106 presymptomatic testing (PT) requests from subjects at risk of ALS/FTD, 65% were seen in the last 3 years. Over two-thirds of the subjects were at risk of carrying mutations responsible for ALS, FTD, or both. Sixty-two percent of the subjects came from families with a known hexanucleotide repeat expansion in C9ORF72. During the same period, we counseled 840 subjects at risk of HD. Subjects at risk of ALS/FTD had the presymptomatic test significantly sooner after being aware of their risk, but were older than those at risk of HD. The youngest subjects requesting the test had the highest disease load in the family (p < 0.05).
Conclusions Demands for PT for ALS/FTD have been increasingly growing, particularly since the discovery of the C9ORF72 gene. The major specificity of the genetic counseling for these diseases is the unpredictability of the clinical phenotype for most of the genes involved. Awareness of this added uncertainty does not prevent individuals from taking the test, as the dropout rate is not higher than that for HD.
Glossary
- ALS/FTD=
- amyotrophic lateral sclerosis and/or frontotemporal dementia;
- HD=
- Huntington disease;
- PT=
- presymptomatic testing
Footnotes
Go to Neurology.org/NG for full disclosures. Funding information is provided at the end of the article.
The Article Processing Charge was funded by the authors.
- Received July 28, 2020.
- Accepted in final form October 20, 2020.
- Copyright © 2020 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the American Academy of Neurology.
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