Pathological assessments for the presence of hexanucleotide repeat expansions in C9ORF72 in Alzheimer's disease

Background: We have sought histological evidence, using TDP-43 and p62 immunohistochemistry, for the presence of expansions in C9ORF72 among 200 patients with pathologically confirmed AD. Results: We noted TDP-43 pathological changes in hippocampus and temporal cortex in 45 (22.5%) of these patients, but did not detect any cases where p62 positive changes in hippocampus and cerebellum, considered pathognomic for C9ORF72 expansions, were present. Conclusion: We conclude that expansions in C9ORF72 associated with AD are a rare occurrence, and in those instances in the literature where these have been reported, the presence of AD may in fact be coincidental and unrelated to the expansion.