Therefore, given the clinical and pathological overlaps between FTD, Parkinsonism syndrome, PD, and Alzheimer’s dementia (AD), the aim of this study was to determine whether the abnormal C9orf72 hexanucleotide repeat expansions found in FTD patients is also associated with these other neurodegenerative disorders in a Taiwanese population. This evidence concerns the gene C9orf72 and Parkinson disease.