Delusional Infestation in Parkinson's Disease.

Delusional infestation (DI), a form of psychosis, has rarely been reported in patients with Parkinson disease (PD). The clinical presentation and successful treatment of DI is illustrated through 5 cases. Each patient developed DI during treatment for moderate to advanced Parkinson's disease, and only 2 had cognitive impairment. Two patients were on monotherapy: 1 on a dopamine agonist and the other on trihexyphenidyl. Three patients were receiving complex combination therapy with 2 to 5 different anti-Parkinsonian medications at the onset of their delusion. Selective discontinuation or reduction of these medications was key to the resolution of DI in each patient. Although the medication adjustments differed, the changes resulted in the reduction of anticholinergic effects or extracellular striatal dopamine levels. This series emphasizes the clinical features and management strategies for this disruptive form of psychosis in patients with PD.