Serum BDNF levels were insignificantly higher in the AD group than in the aMCI group controls. BDNF was insignificantly different in genotype and allele distribution between the three groups and did not significantly affect MMSE score in AD and aMCI. Further investigation is needed to examine the potential of BDNF as an AD biomarker. The gene discussed is BDNF; the disease is Alzheimer disease.