 Some parasites are real, and some are not. Delusional parasitosis is a form of psychosis characterized by the false belief that you're infested with some sort of parasite. It can be triggered by a variety of brain diseases, such as schizophrenia, dementia, due to vitamin B12 deficiency, stroke. Tragic case report. A woman who suddenly started repeatedly washing her clothes with bleach until she ruined them, scratching her whole body up. She was hospitalized, persistently expressing her delusions of parasitosis. They did an MRI, and what did they find causing these delusions? An actual pork tapeworm in her brain. A tragic case that was tragically ironic. The first report of brain parasitosis as an underlying neurological condition in delusional parasitosis.