Psych for the ABIM: Know these Medical Illnesses Masquerading as Psychosis

Editor’s Note: Anyone who thinks that psychiatry is a distinct field from medicine and thus not covered on the ABIM Internal Medicine Board exam is mistaken. In fact, the ABIM exam blueprint lists Psychiatry as comprising 4% of the exam, the same as Neurology and more than Dermatology. In her second blog post, Psychiatrist Esther Oh, MD breaks down medical illnesses that cause psychosis.


Psychosis can be the presenting symptom for many medical problems, including hallucinations, delusions, and disorganized thought. Differentiating between psychosis secondary to a medical condition versus a primary psychotic disorder can often be a challenge. It is crucial to have this skill as many of the former cases can be life-threatening yet treatable.


Red flags that may indicate an organic disease for a patient’s psychotic symptoms:
  • 40+ years old with no previous psychiatric diagnosis
  • Distinct visual hallucinations with vivid colors that change
  • Olfactory hallucinations
  • Illusions (misinterpretations of stimuli; not the same as hallucinations, which are perceptions created in the absence of any stimuli)
  • Recent head injury


Patients who are psychotic can be unpredictable, uncooperative and even aggressive, making it difficult to exam them. Ideally you want to complete a thorough neurological exam, but if that’s not possible, completing even a basic neurological exam to rule out medical causes will help:
  • Observe their gait and body movements (check for any weakness, paralysis, ataxia, choreoathetoid movements)
  • Complete an eye exam. Check the extraocular movements, see if the pupils are equal and reactive to light and check for any vertical or horizontal nystagmus. Horizontal nystagmus can be a red flag for drug intoxication. Be aware that it is never a normal finding in a patient with pure psychosis.
  • Observe speech for any slurring, aphasias, or word finding difficulties


Another tricky part about diagnosing psychosis is ruling out delirium in an acute medical setting since it can be a medical emergency that has specific etiologies and treatment regimens. Delirium can present with symptoms such as disorientation, memory impairment, fluctuation or impairment in level of consciousness, labile affect, impaired judgment or insight, abnormal autonomic signs (tachycardia, fever, diaphoretic, hypertension), agitation, and even paranoia. Possible causes include:
  • Hypoglycemia: can present with coma, anxiety, or tremors. Treatment is to give some candy or orange juice
  • Diabetic ketosis: notable for the sweet smell of acetone on their breath with history of diabetes
  • Wernicke- Korsakoff syndrome: acute thiamine (Vitamin B1) deficiency, commonly seen in patients with alcohol dependence that can cause rapid brain damage. Symptoms include nystagmus, cerebellar ataxia, ocular palsies, and hallucinations. Treatment is to give thiamine 100mg IM.
  • Delirium tremens (DTs): caused by withdrawal of alcohol or other sedative-hypnotic medications. Symptoms include elevated autonomic signs, agitation, and visual and tactile hallucinations usually with a history of abuse and recent (3-4 days) decrease in intake.
  • Meningitis: look for a stiff neck and fever
  • Subdural hematoma: usually occurs after a traumatic brain injury and can present with fluctuation in consciousness, slurred speech, ataxia, and headache
  • Subarachnoid hemorrhage: delirium with fluctuation in consciousness, throbbing headache, and stiff neck.
  • Anticholinergic poisoning: delirium caused by an overdose of tricyclic antidepressants, over-the-counter drugs, or organophosphate insecticides. Look for flushing, dry mouth, dilated pupils, and cardiac arrhythmias.


There are numerous potential medical causes for psychosis but the most concerning and/or common etiologies are:

Neurologic diseases
  • Huntington’s chorea: an autosomal dominant neurodegenerative disorder with choreiform movements, mood and psychotic symptoms, and cognitive decline. Sometimes the initial presentation can be psychosis which occurs in 5-16% of patients.
  • Alzheimer’s disease: most common cause of progressive dementia that can presents in the later stages with delusions, paranoia, and visual hallucinations.
  • Temporal lobe epilepsy: especially partial complex seizures along with ictal and postictal states can present with disorganized thought, delusions, and aggression.
  • Parkinson’s disease: the most common psychotic symptom is visual hallucinations which can occur in up to 30% of patient.

Central Nervous System (CNS) infections
  • Encephalitis: vaguely known as the acute inflammation of the brain. The most common cause of psychiatric issues is herpes simplex virus (HSV) encephalitis. It can present with fever, seizures, psychosis, fluctuating mental status, and bizarre, inconsistent behavior.
  • Neurosyphilis: an infection of the brain and/or spinal cord caused by the bacterium Treponema pallidum which usually occurs after 10 to 20 years of chronic, untreated syphilis. Look for Argyll Robertson pupils.
  • HIV encephalopathy/dementia: neurocognitive issues are more likely in patients who are not receiving appropriate HAART treatment or have low CD4 counts. It can present with delirium and paranoia.

Drugs that can contribute to psychotic symptoms
  • Illicit drugs such as methamphetamine, cocaine, hallucinogens, ecstasy, and marijuana.
  • Prescribed medications such as stimulants, opioids, and steroids are the most common
  • Alcoholic hallucinosis: a complication of alcohol withdrawal that can present with auditory (most common) and visual hallucinations in a clear sensorium in the context of recent cessation or decrease in alcohol use.

Other diseases
  • Acute intermittent porphyria: an autosomal dominant disorder that can present with frank psychosis. The classic form can present with the triad of symptoms including colicky abdominal pain, motor polyneuropathy, and psychosis. It is important that those patients avoid using barbiturates which can precipitate attacks.
  • Wilson’s disease: hepato-lenticular degenerative, autosomal recessive disorder in which cooper accumulates in the tissues. Look for Kayser-Fleischer rings on the eye exam and low serum ceruloplasmin level.
  • Lupus cerebritis: inflammation of the cerebrum which can cause psychosis in lupus patients who are treated with steroid therapy. Interestingly, many improve with an increase in steroid dose. Make sure to rule out any infectious etiologies for psychosis as a fever may be masked by the use of steroids.
  • Brain tumor: occipital lesions can cause visual hallucinations, temporal lesions can cause auditory hallucinations. The visual pathway crosses the temporal, parietal, and occipital lobes and therefore visual hallucinations can occur with a lesion in any one of these locations.

Though psychotic symptoms are often associated with schizophrenia, keep in mind psychotic symptoms can also be caused by medical illnesses. The goal in those cases is to first treat the underlying medical cause. If psychotic symptoms do persist, it can be helpful to start anti-psychotic agents, such as haloperidol, olanzapine, risperidone, or aripiprazole. The key is to start with low doses and be mindful of the potential side effect profile including sedation, weight gain, dizziness, and extrapyramidal symptoms.


Dr. Oh is currently a child and adolescent psychiatry fellow at the University of California in Los Angeles. She completed her adult psychiatry residency at Harbor-UCLA Medical Center in Torrance, CA. She obtained her medical degree from the David Geffen School of Medicine at UCLA. Dr. Oh is interested in reducing stigma against mental health and increasing the awareness and acceptance of treatment especially within the Asian community. Her previous post in this series covered the barriers between psychiatry and internal medicine.


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