Late-onset obsessive-compulsive disorder as the initial manifestation of possible behavioural variant Alzheimer's disease.

Introduction: A late-onset obsessive-compulsive disorder (OCD) might be a challenging diagnostic issue because of the overlapping with the dementia conditions more related to frontal lobe pathology. We aim to describe and investigate how this condition might represent the isolated long-lasting symptomatology of a frontal Alzheimer's disease (AD).

Methods: An elderly woman with normal cognitive status showed a subacute onset of OCD with contamination obsession and washing compulsion. We conducted neuropsychological assessments and neuroimaging examinations at the onset and at 3-years follow-up.

Results: At 3-years follow-up, the patient developed cognitive deterioration, frontal behavioural disorders and improvement of OCD. Cognitive assessment showed impairments of executive functions, episodic memory, and constructional apraxia, according to the involvement of fronto-mesial, temporal and parietal regions at neuroimaging. A clinical diagnosis of possible behavioural variant AD was assigned.

Conclusion: A typical OCD might be the long-lasting initial manifestation of a possible behavioural variant AD due to dysfunctions of the anterior cingulate network.