A person of 35 years is having a firm belief about infidelity involving the spouse. And he never allows her to go out of home alone. He often locks his house, while going office. Despite all this, he is persistently suspicious about her character. The probable diagnosis is-

D i.e. Othello SyndromeThis person is having the disorder as he is having persistent delusion of infidelity without other personality disturbance, and hallucination (so schizophrenia is ruled out).Delusional disorders are differentiated from Schizophrenia by the presence of systematic delusions (Bizarre in Schizophrenia) with the absence of hallucinations, near normal personality (only disturbed in the delusional area), & contact with reality (only disturbed in the delusional area).