We found that both MCI and AD subjects showed lower BDNF serum levels and higher cathepsin D, IgE, neuropilin-1, ANG-2, FXI, EGFR, VEGFA, ICAM-1, MMP-9, vWF, haptoglobin, and p-Tau181 serum levels than controls. The gene discussed is CTSD; the disease is Alzheimer disease.