Clinical Vignette
Patient: "Mrs. W," 48-year-old office manager with no prior psychiatric history, brought to the emergency department by her husband after 1 week of visual hallucinations and disorganized behavior.
Chief Concern: Husband: "She's seeing people in our house who aren't there. She's confused, can't follow conversations, and she forgot how to use the coffee maker yesterday."
History of Present Illness: Mrs. W had been in excellent health until approximately 3 weeks ago when she began complaining of fatigue and difficulty concentrating. Over the following 2 weeks, her husband noted increasing confusion, word-finding difficulties, and intermittent disorientation (getting lost in her own neighborhood). One week ago, she began reporting visual hallucinations (seeing 'a woman standing in the kitchen' and 'shadows moving on the walls'). She became frightened and agitated. Her behavior became disorganized: she placed groceries in the bathroom, wore her coat inside-out, and could not follow multi-step instructions. She has no psychiatric history, no family history of psychotic disorders, and no substance use. She takes levothyroxine 100mcg daily for hypothyroidism diagnosed 5 years ago. Her last thyroid labs were 8 months ago (normal at that time).
Medical History: Hypothyroidism (5 years, on levothyroxine). No other medical conditions. No recent medication changes. No recent illnesses or surgeries.
Mental Status Exam: Appears confused. Speech slowed with word-finding pauses. Oriented to person, partially oriented to place (knows she is in a hospital but not which one), disoriented to date. Reports seeing 'the woman again, behind you' (visual hallucination during interview). No auditory hallucinations. No systematized delusions. Attention impaired (unable to spell WORLD backwards). Memory impaired (0/3 recall at 5 minutes). Affect fearful. No insight into the abnormality of her experiences.
Step 1: Applying the DSM-5-TR Hierarchical Exclusion
DSM-5-TR requires ruling out substance and medical etiologies before diagnosing a primary psychotic disorder. In this case, several features mandate a thorough medical workup before considering Schizophrenia or other primary psychotic diagnoses:
Red flag 1: Late onset without psychiatric history
Age 48, no prior psychiatric symptoms, no family history. Late onset of psychosis without prodrome is atypical for Schizophrenia (typical onset: late adolescence to early 30s). ORGANIC ETIOLOGY MUST BE EXCLUDED.
Red flag 2: Visual hallucinations
Visual hallucinations are a marker for organic etiology (medical, neurological, or substance-related). Primary psychiatric psychosis more commonly produces auditory hallucinations. ORGANIC ETIOLOGY MUST BE EXCLUDED.
Red flag 3: Cognitive impairment
Disorientation, memory impairment, attention deficits, and executive dysfunction (cannot follow multi-step tasks). Cognitive decline of this nature is atypical in primary psychotic disorders at onset. ORGANIC ETIOLOGY MUST BE EXCLUDED.
Red flag 4: Acute onset with rapid progression
Progression from normal functioning to frank psychosis and cognitive impairment over 3 weeks. This rapid trajectory is more consistent with a medical process than a primary psychiatric disorder. ORGANIC ETIOLOGY MUST BE EXCLUDED.
Step 2: Medical Differential Diagnosis
| Etiology | Supporting Features | Workup Required | Assessment |
|---|---|---|---|
| Thyroid dysfunction (myxedema psychosis) | Known hypothyroidism on levothyroxine. Labs 8 months old. Fatigue and cognitive changes preceded psychosis. | STAT TSH, free T4 | High priority: subtherapeutic levothyroxine can cause severe hypothyroidism with psychotic features |
| Autoimmune encephalitis (anti-NMDAR) | Subacute onset of psychiatric symptoms + cognitive decline in a middle-aged woman. | CSF analysis, NMDAR antibodies, brain MRI | Must be excluded: treatable cause of psychosis + cognitive decline |
| Delirium | Fluctuating attention, disorientation, acute onset. | CBC, CMP, UA, blood cultures, EEG | Must be excluded: cognitive and attentional features suggest delirium component |
| Neurodegenerative (early dementia with Lewy bodies) | Visual hallucinations + cognitive decline + fluctuating attention. | Brain MRI, neuropsych testing, DAT scan | Possible but onset is more acute than typical DLB |
| Structural (brain lesion/tumor) | New-onset psychosis and cognitive changes. | Brain MRI with contrast | Must be excluded |
Medical Workup Priority
The immediate priorities are: (1) STAT thyroid function tests (given known hypothyroidism and 8-month gap in monitoring), (2) comprehensive metabolic panel, CBC, urinalysis to exclude delirium, (3) brain MRI with contrast, (4) consideration of lumbar puncture for autoimmune encephalitis antibodies if initial workup is unrevealing.
Step 3: DSM-5-TR Criteria for Psychotic Disorder Due to Another Medical Condition
Criterion A: Prominent hallucinations or delusions.
Prominent visual hallucinations (formed images of people). Disorganized behavior. No systematized delusions. MET.
Criterion B: Evidence from history, physical exam, or laboratory findings that the disturbance is the direct pathophysiological consequence of another medical condition.
Pending medical workup. The clinical presentation (late onset, visual hallucinations, cognitive impairment, rapid progression, known thyroid disease) strongly suggests a medical etiology. PENDING WORKUP.
Criterion C: Not better explained by another mental disorder.
Features are atypical for primary psychotic disorders (late onset, visual hallucinations, cognitive impairment, no prodrome). MET.
Criterion D: Does not occur exclusively during delirium.
Some features overlap with delirium (fluctuating attention, disorientation), but psychotic symptoms appear to persist beyond attentional fluctuations. Concurrent delirium cannot be excluded. REQUIRES CLARIFICATION.
Diagnostic Formulation
Diagnostic Conclusion
Provisional: Psychotic Disorder Due to Another Medical Condition (F06.2): Clinical presentation is most consistent with an organic etiology for psychosis. Four red flags for medical cause identified (late onset, visual hallucinations, cognitive impairment, rapid progression). Known hypothyroidism with 8-month lab gap provides a plausible medical cause. Final diagnosis pending completion of thyroid function tests, brain MRI, and metabolic workup. If severe hypothyroidism is confirmed, myxedema psychosis is the likely diagnosis. If workup reveals anti-NMDAR antibodies, autoimmune encephalitis becomes the diagnosis.
Teaching Points
- The mnemonic 'VINDICATE' helps organize the medical differential for new-onset psychosis: Vascular, Infectious, Neoplastic, Degenerative, Intoxication/withdrawal, Congenital, Autoimmune, Traumatic, Endocrine. Every first-episode psychosis presentation requires consideration of these categories.
- Visual hallucinations in a patient with no prior psychiatric history are organic until proven otherwise. Primary psychiatric psychosis is predominantly associated with auditory hallucinations. Visual hallucinations should trigger a medical workup.
- Thyroid dysfunction is a treatable and reversible cause of psychosis. Severe hypothyroidism (myxedema) can produce psychotic symptoms (myxedema madness), cognitive impairment, and behavioral changes. The treatment is thyroid hormone replacement, not antipsychotics.
- Anti-NMDA receptor encephalitis is an increasingly recognized cause of psychiatric symptoms in young and middle-aged women. The classic presentation involves psychiatric symptoms (psychosis, agitation, personality change), cognitive decline, seizures, and movement disorders. It is treatable with immunotherapy.
- DSM-5-TR Criterion B requires establishing a direct pathophysiological relationship between the medical condition and the psychotic symptoms. This is supported by temporal correlation (symptoms began after medical condition onset or worsening), atypical features for primary psychosis, and resolution of psychiatric symptoms with treatment of the medical condition.