C9orf72 and Alzheimer disease: Patients with FTD-ALS C9orf72 also have a higher rate of family psychiatric history17 which can lead to clinical bias and misdiagnosis.16 Furthermore, C9orf72 gene expansions have also been identified as rare causes of other neurodegenerative phenotypes,18 including in 1% of Parkinson’s disease and Alzheimer’s disease,3,4 progressive supranuclear palsy, ataxic syndromes, corticobasal syndrome, Huntington disease-like syndrome, and Creutzfeldt-Jacob disease.