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Psychosis associated with expansions in the C9orf72 gene: the influence of a 10 base pair gene deletion
  1. Julie S Snowden1,2,
  2. Jennifer Harris1,2,
  3. Jennifer Adams1,2,
  4. Jennifer C Thompson1,2,
  5. Anna M Richardson1,2,
  6. Matthew S Jones1,2,
  7. David Neary1,
  8. Yvonne S Davidson2,
  9. Andrew C Robinson2,
  10. Sara Rollinson2,
  11. Stuart Pickering-Brown2,
  12. David M Mann2
  1. 1Cerebral Function Unit, Manchester Academic Health Sciences Centre, Greater Manchester Neuroscience Centre, Salford Royal NHS Foundation Trust, Salford, UK
  2. 2Faculty of Human and Medical Sciences, Institute of Brain, Behaviour and Mental Health, University of Manchester, Manchester, UK
  1. Correspondence to Professor Julie S Snowden, Cerebral Function Unit, Greater Manchester Neuroscience Centre, Salford Royal Foundation Trust, Salford, M6 8HD, UK; julie.snowden{at}

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We previously reported1 that expansions in the C9orf72 gene, identified by Southern blotting or using a repeat primed PCR assay,2 may go undetected using an alternative, standard PCR assay.3 We attributed this discrepancy to a 10 base pair deletion adjacent to the expansion which was presumed to interfere with genotyping.1 To determine the possible clinical and pathological relevance of the deletion, we compared patients in whom the C9orf72 expansion was detected using the Renton3 assay (C9 reference group) with those carrying an expansion not detected by this method (deletion group).


The criteria for inclusion in the study were: (A) patients had been investigated and diagnosed with dementia within a single, specialist dementia clinic, (B) they had donated DNA as part of an ethically approved study into the molecular genetics of dementia and (C) expansions in the C9orf72 gene were identified using one or more standard procedures.1–3 An additional patient, in whom pathological examination showed p62 positive neuronal inclusions immunoreactive for the dipeptide repeat proteins, poly-GA, poly-GP and poly-GR, was also included since such histological findings are considered pathognomonic of the presence of an expansion in C9orf72.4 …

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