Regarding the usefulness of CSF biomarkers in the differential diagnosis of FTLD vs. AD, an interesting review by D Irwin, J Trojanowski, and M Grossman highlight that CSF measurements of Aβ 1-42, t-tau, and p-tau differ significantly in FTLD from the abnormal levels seen in AD, and in a subset of both FTLD-tau and FTLD-TDP there are extremely low levels of t-tau of unclear etiology (Irwin et al., 2013). This evidence concerns the gene MAPT and Alzheimer disease.