APOE and Alzheimer disease: That is not 100%, despite that the two drugs probably provide benefits to most causes of AD because the underpinnings of AD are several and disparate—familial, deposition of amyloid and/or hyperphosphorylated tau, diabetes, cerebrovascular disease, possession of the APOE ε4 allele, trisomy 21, environmental toxins, etc.; and there might be unknown others with different underpinnings.