APOE and Alzheimer disease: Comment: This patient was atypical for type 3 Alzheimer's disease in his late age of onset, but was in all other respects typical, including a cortical presentation with aphasia and dyscalculia, ApoE ε4-negative genotype, lack of family history (except in the tenth decade), neuropsychological testing suggesting an atypical presentation for Alzheimer's, with CSF indicative of Alzheimer's disease.