Isolated delusional syndrome in Parkinson's Disease.

Psychotic features in patients with Parkinson's Disease usually present as visual hallucinations against a background of cognitive deterioration and dopaminomimetic therapy. Isolated delusions are rare. We report here 4 patients with Parkinson's Disease who developed a delusional syndrome resembling schizophreniform psychosis in the absence of changes in alertness, visual hallucinations or dementia. We suggest that this syndrome may be more common than previously recognized, and that it may be related to the use of dopaminergic medications and environmental triggers on a background of a susceptible individual. This syndrome suggests interesting parallels with the pathophysiology of amphetamine-induced psychosis and schizophrenia.