BACE1 and Alzheimer disease: In conclusion, the results of this study suggest that the G/C (rs638405) polymorphism of BACE1 gene might not be related with sporadic AD in Khuzestan, Isfahan and Fars provinces in Iran, and the BACE1 gene CC genotype frequency or C allele frequency might be a genetic risk factor for developing AD in Khuzestan, Isfahan and Fars provinces in Iran.