CTSD and Alzheimer disease: [29] Specifically there was an increase in the number of senile plaques containing Aβ40 in the brain associated with the T allelic variant of cathepsin D. This variant is thought to have a greater beta-secretase activity than the C variant therefore yielding more of the cleaved Aβ which in turn may accelerate AD pathogenesis by seeding amyloid formation [23,29,35].