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C9orf72 – FTD-ALS Spectrum — SCE Neurology MCQ

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HardNeurodegenerative DiseaseC9orf72 – FTD-ALS SpectrumSCE Neurology

A 50-year-old with behavioural-variant frontotemporal dementia has a C9orf72 hexanucleotide repeat expansion. Her father had amyotrophic lateral sclerosis. Which statement is most appropriate when counselling first-degree adult relatives?

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Correct answer: C — The expansion is inherited in an autosomal-dominant pattern with age-dependent incomplete penetrance

C9orf72 expansions cause an autosomal-dominant FTD–ALS spectrum with age-dependent incomplete penetrance. Relatives should be offered formal genetic counselling before predictive testing; a result has implications for both FTD and motor-neurone disease risk.

Reference: Genomics Education Programme, C9orf72-related frontotemporal dementia and amyotrophic lateral sclerosis: https://www.genomicseducation.hee.nhs.uk/