Rapid Decline showed the most severe clinico-pathological profile, with elevated β-amyloid, tau, TDP-43, and CAA, along with higher prevalence of AD dementia, pathological AD, APOEε4 carriers, atherosclerosis, hippocampal sclerosis, neocortical Lewy bodies, and dementia with Lewy bodies. The gene discussed is MAPT; the disease is Alzheimer disease.