Delusional Infestation Secondary to the Dopamine Agonist Ropirinole in a Patient With Parkinson's Disease: A Case Report With an Outline of the Biology of Psychosis

Delusional infestation (DI) is a thought disorder, a delusion that one is infested with pathogens. Remarkably, these patients do not typically exhibit symptoms of anxiety or depression. The role of the dopamine D2 receptor is central to the idea of psychosis. In this article, we present a case of ropirinole-induced delusional skin infestation in a patient with Parkinson's disease, that was reversible with drug discontinuation. We seize upon this opportunity to discuss the pathology of the dopamine receptors, the glutamate N-methyl D-aspartate (NMDA) receptors and the serotonin 5-hydroxytryptamine (5HT-2A) receptors in the generation of psychosis. We outline the fundamental pharmacodynamical differences between the typical and atypical anti-psychotics that will help us understand how these agents work favorably and adversely. We also briefly review the neuroradialogy of psychosis and adumbrate on the mismatch between the meso-limbic system (motivational) and the salience network (valence) as the driver of the psychotic phenomenon.