[Neurosyphilis and cognitive disorders].

We report the case of a 75 year old man, admitted for a delirium which was unusual by its severity and duration. Underlying disorders were an infectious disease (neurosyphilis) and prodromal Alzheimer's disease. This association was thought to be responsible for the delirium intensity. According to a literature review, we discuss the difficulties of cerebral neurosyphilis diagnosis, its cognitive and behavioural symptoms. We also discuss the cumulative effects of multi morbidities on clinical presentation, underlining a frequent problem in elderly patients in whom multiple causes of cognitive impairment often coexist.