The main symptom is a persistent delusion or delusions (a fixed belief) – for example, about a situation, condition or action – that is not happening but may be plausible in real life. Types include:
Erotomanic – Delusion of a special, loving relationship with another person, usually someone famous or of higher standing. (This kind of delusion is sometimes at the root of stalking behavior.)
Grandiose – Delusion that the person has a special power or ability, or a special relationship with a powerful person or figure, such as the president, a celebrity or the Pope.
Jealous – Delusion that a sexual partner is being unfaithful.
Persecutory – Delusion that the person is being threatened or maltreated.
Somatic – Delusion of having a physical illness or defect.