AK2 and Alzheimer disease: Within the 400 CSF features, 18 analytes were specific to AD (such as GDA, PDE6D, FN1), seven to PD (SEMA4B, TNFSF8), and three to FTD (VSIG2, GLIPR1, IGFBP4), whereas 147 (AK2, EIF3G, MDH1) were shared by all diseases (Fig. 2C&E).