Differential Diagnosis

Bipolar disorder: Grandiose and/or paranoid delusions can be seen in the manic phase of bipolar disorder. Other prominent symptoms include decreased need for sleep, increased goal-directed activity, increased rate of speech.
Delirium: Hallucinations, particularly visual hallucinations, can be a symptom of delirium, even when it is mild. The onset of delirium is typically acute, and there is usually an identifiable metabolic, pharmacologic, or infectious cause. The mental status examination reveals multiple cognitive impairments and a diminished or waxing and waning level of consciousness.
Dementia: Alzheimer disease with prominent frontal symptoms or frontotemporal dementia can be confused with late-onset schizophrenia, as it can involve features of socially inappropriate, objectionable, and odd behaviors as well as premorbidly odd or “schizoid” personality features. Lewy body dementia usually presents with visual hallucinations in the context of autonomic instability, parkinsonism, and frequent falls.
Medications/drugs: eg, anticholinergics, antiparkinsonian agents, benzodiazepines or alcohol (including withdrawal), cardiac medications (eg, digitalis), corticosteroids, opioid analgesics, stimulants.
Late-onset delusional (paranoid) disorder or late onset schizophrenia.
Major depression: Delusions in major depressive disorder usually reflect self-deprecation, self-blame, hopelessness, or the conviction of ill health.
Physical disorders: hypo- or hyperglycemia, hypo- or hyperthyroidism, sodium or potassium imbalance, Cushings syndrome, Parkinsons disease, B12 deficiency, sleep deprivation, AIDS
Pain, untreated
Schizophrenia
Structural brain lesions: tumor or stroke
Seizure disorder: eg, temporal lobe