Snapshot A 47-year old woman is brought to the emergency department by the local sheriff. She was arrested earlier in the night for trespassing on the lawn of her neighbor. The patient states in an agitated tone that she was not trespassing, and her neighbor "is in love" with her and had asked her to come over that night. The physician obtains the contact information of the patient's neighbor and upon questioning, he states that he does not even know the patient's last name, and she has been bothering him for the last 6 weeks ever since he moved to the neighborhood. The patient is alert and oriented on mental status examination and denies having any auditory or visual hallucinations. Introduction Overview delusional disorder characterized by > 1 month of delusions without other psychotic symptoms Epidemiology prevalence 0.02% in the US demographics mean age of onset is 40 years females > males Pathophysiology unknown may involve biochemical and psychological factors Associated conditions shared psychotic disorder (folie à deux) development of delusions in a person in a close relationship with someone with delusional disorder often resolves upon separation Presentation Symptoms delusions false beliefs based on incorrect inference about reality typically non-bizarre (i.e., unlikely but possible) patient typically lack insight to the fact that their beliefs are delusions types of delusions include persecutory belief one is going to be harmed referential belief that certain gestures, comments, or environmental cues are directed at oneself grandiose belief that the individual has exceptional abilities, wealth, or fame nihilistic conviction that a major catastrophe will occur somatic beliefs focused on bodily function or sensation erotomanic false belief that another individual is in love with them Physical exam normal cognitive function criteria for diagnosing delusional disorder presence of 1 or more delusions for > 1 month the criteria for schizophrenia has never been met before functioning is not markedly impaired if manic or major depressive episodes have occurred, these have been brief relative to the duration of the delusional periods the disturbance is not better explained by another mental disorder (i.e., OCD) or substance use disorder Differential Delirium key distinguishing factors fluctuating level of consciousness, altered sleep/wake cycle, hallucinations, and impaired cognition Dementia key distinguishing factor impaired cognition Schizophrenia key distinguishing factor disorganized thought process, speech, or behaviors Body dysmorphic disorder key distinguishing factor obsessive focus on perceived flaw in appearance and excessive attempts to fix the flaw Treatment Lifestyle cognitive-behavioral therapy supportive therapy to educate patients about the illness and social skills training (i.e., not discussing delusional beliefs in public) Medical antipsychotics (i.e. aripiprazole and ziprasidone) first-line treatment of delusional disorder requires significant effort to provide information about the medication, the side effects, and length of treatment patient denial and lack of insight may present as obstacles to treatment