A 73-year-old woman is brought to the office by her son due to a change in behavior and increasing forgetfulness. Over the past 2 days the patient has become more irritable, has been unable to sleep, and has uncharacteristically forgotten to pick up the mail or feed her dogs. When interviewed, the patient appears to be distracted as if responding to internal stimuli. During the examination, she shouts at the nurse, "Get out of my house! Where did you thieves take my clothing?" Several minutes later she appears drowsy. The patient has forgotten people's names and had word-finding difficulties over the last year, but the son was not initially concerned because she lived independently, shopped, cooked, and handled her own finances without difficulty. Temperature is 38.3 C (101 F), blood pressure is 140/90 mm Hg, pulse is 118/min, and respirations are 18/min. Laboratory results are as follows:
| Complete blood count | |
| Hemoglobin | 14 g/dL |
| Platelets | 280,000/mm3 |
| Leukocytes | 15,500/mm3 |
| Urinalysis | |
| Blood | negative |
| Glucose | negative |
| Ketones | negative |
| Leukocyte esterase | positive |
| Nitrites | positive |
| White blood cells | 50/hpf |
| Red blood cells | 9/hpf |
Which of the following is the most likely diagnosis in this patient?
Delirium is characterized by a fluctuating disturbance in attention and arousal (eg, from shouting to drowsy within minutes) that can develop acutely in the context of an underlying medical illness. It is common postoperatively or in the setting of new or worsening infections (eg, urinary tract infection, as in this patient). Delirium may also occur after the introduction of new medications (eg, opioids, benzodiazepines, anticholinergics). The elderly are at higher risk for delirium.
Delirium may be associated with psychotic symptoms, particularly visual hallucinations, in addition to sleep and behavioral changes. Symptoms of fluctuating cognitive impairment and acute onset in the context of an underlying condition can help differentiate delirium-induced psychosis from primary psychotic disorders (in which the sensorium is clear). Although antipsychotics can be used to target the psychotic manifestations of delirium, primary treatment is the identification and treatment of the underlying condition.
(Choices A and D) For a diagnosis of dementia (eg, Alzheimer disease, dementia with Lewy bodies), a patient must have impairment in activities of daily living (eg, meal preparation, shopping, bathing) as a result of cognitive impairment. Dementia is an insidious disease that develops slowly over an extended period. This patient has relatively age-normative premorbid cognitive symptoms and preservation of activities of daily living. The acute worsening of her cognitive impairment is due to delirium superimposed on age-related cognitive changes.
(Choice B) Brief psychotic disorder is characterized by a brief duration (≥1 day but <1 month) of psychotic symptoms. However, this diagnosis is excluded if the psychotic symptoms are better explained by the effects of a medication or medical illness (eg, delirium in the context of a urinary tract infection). Patients with brief psychotic disorder are typically fully oriented and have a clear sensorium.
(Choice E) To diagnose psychotic disorder due to a medical condition, delirium must be absent; in addition, there must be a causal link between psychotic symptoms and a medical condition (eg, hallucinations due to a brain tumor), and the psychosis cannot be better explained by another condition (eg, schizophrenia). This patient's psychotic symptoms (eg, persecutory delusion) occur in the context of delirium; therefore, a diagnosis of psychotic disorder due to a medical condition cannot be made.
Educational objective:
Delirium-induced psychosis is differentiated from primary psychotic disorders by fluctuating levels of consciousness, acute onset, and association with an underlying condition and/or offending medications.