MAPT and Alzheimer disease: This case also illustrates a number of clinical and neuropsychological issues: the significance of anomia in the context of atypical amnesia in pointing toward a non-AD diagnosis; the value of searching for a MAPT mutation in cases of early onset dementia characterized by amnesia and relevant family history with negative familial AD mutations; the complexity in differentiating organic and functional amnesia and the unique effect on autobiographical memory as a result of an interaction between damaged episodic and semantic memory systems.