encapsulated delusion

en·cap·su·lat·ed de·lu·sion

a delusion that usually relates to one specific topic or belief but does not pervade a person's life or level of functioning.
Farlex Partner Medical Dictionary © Farlex 2012

encapsulated delusion

An isolated mistaken but unshakable belief in something for which there is neither evidence nor common acceptance, occurring in the absence of other signs or symptoms of psychiatric illness.
Medical Dictionary, © 2009 Farlex and Partners