PSEN1 and Alzheimer disease: Another study identified a ∼25 kDa η-CTF in CSF, but in this case the peptide content was higher in AD patients with a PSEN1 familial mutation, in patients with sporadic AD and in Down Syndrome individuals with Alzheimer’s type dementia, compared to age-matched non-demented controls, raising the possibility that η-CTF could be a new disease biomarker (Garcia-Ayllon et al., 2017).