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Who and Why? Requests for Presymptomatic Genetic Testing for Amyotrophic Lateral Sclerosis/Frontotemporal Dementia vs
Maria Del Mar Amador1, Marcela Gargiulo1, Christilla Boucher1
1Maria del Mar Amador, Département de Neurologie (M.d.M.A., F.S.), Centre de Référence SLA de Paris, Assistance Publique-Hôpitaux de Paris, Sorbonne Université Hospital Pitié-Salpêtrière, Paris, France; Département de Génétique (M.d.M.A., M.G., C.B., A.H., S.S., A.D.), Assistance Publique-Hôpitaux de Paris, Sorbonne Université, Sorbonne Université Hospital Pitié-Salpêtrière, Paris, France; Laboratory of Clinical Psychology (M.G.), Psychopathology and Psychoanalysis PCPP, EA 4056, University Paris Descartes, Sorbonne Paris City, Psychology Institute, Boulogne-Billancourt, France; Département de Génétique (F.C., C.C.), UF de Neurogénétique, Assistance Publique-Hôpitaux de Paris, Sorbonne Université Hospital Pitié-Salpêtrière; Centre de Référence des Démences Rares ou Précoces (I.L.B.), IM2A, Département de Neurologie, Assistance Publique-Hôpitaux de Paris, Sorbonne Université Hospital Pitié-Salpêtrière, Paris, France; and Sorbonne Université, Institut du Cerveau et de la Moelle épinière (ICM) (I.L.B., A.D.), Assistance Publique-Hôpitaux de Paris, INSERM, CNRS, Sorbonne Université Hospital Pitié-Salpêtrière, Paris, France.
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.
