title: Lack of c9orf72 repeat expansion in taiwanese patients with mixed neurodegenerative disorders.
abstract: BACKGROUND
  The hexanucleotide repeat expansion in intron 1 of the C9orf72 gene is recognized as the most common genetic cause of frontotemporal dementia (FTD). There are overlapping clinical and pathological characteristics between FTD and Parkinsonism syndrome, and some FTD patients may present with Parkinsonism. The aim of this study was to analyze the hexanucleotide repeat numbers of C9orf72 gene in a mixed Taiwanese cohort with FTD, Parkinsonism syndrome, Parkinson's disease (PD), and Alzheimer's dementia (AD).
  
  
  METHODS
  The number of hexanucleotide repeats was estimated in a total of 482 patients with mixed neurodegenerative disorders and 485 control subjects, using a two-step repeat-primed polymerase chain reaction-based genotyping strategy. The individual groups of patients included patients with Parkinsonism syndrome (n = 95), familial PD (n = 109), young-onset PD (n = 201), FTD (n = 9), sporadic AD (n = 61), and early-onset AD (n = 7).
  
  
  RESULTS
  We did not identify any pathogenic repeats (>30 repeats) of C9orf72 in either the patients or control subjects. However, we found one young-onset PD patient and one control subject that each had an intermediate number of repeats (25 and 21 repeats, respectively). The clinical phenotype of the young-onset PD in this patient was similar to typical idiopathic PD without additional features, and the patient responded well to levodopa treatment.
  
  
  CONCLUSIONS
  The repeat expansion in C9orf72 is not a common cause of PD, Parkinsonism syndrome, or dementia in our population. Further studies are needed to investigate the clinical and biological significance of intermediate repeats in C9orf72.
authors.affiliation: Department of Neurology, College of Medicine, National Taiwan University Hospital, National Taiwan University , Taipei , Taiwan.
authors.forename: Chin-Hsien
authors.initials: CH
authors.lastname: Lin
authors.affiliation: Department of Neurology, College of Medicine, National Taiwan University Hospital, National Taiwan University , Taipei , Taiwan.
authors.forename: Ta-Fu
authors.initials: TF
authors.lastname: Chen
authors.affiliation: Department of Neurology, College of Medicine, National Taiwan University Hospital, National Taiwan University , Taipei , Taiwan.
authors.forename: Ming-Jang
authors.initials: MJ
authors.lastname: Chiu
authors.affiliation: Department of Neurology, College of Medicine, National Taiwan University Hospital, National Taiwan University , Taipei , Taiwan.
authors.forename: Han-I
authors.initials: HI
authors.lastname: Lin
authors.affiliation: Department of Neurology, College of Medicine, National Taiwan University Hospital, National Taiwan University , Taipei , Taiwan.
authors.forename: Ruey-Meei
authors.initials: RM
authors.lastname: Wu
keywords: Alzheimer’s dementia; C9orf72; Parkinsonism; Parkinson’s disease; frontotemporal dementia; risk factor