A 19-year-old previously healthy female is brought to the ER by her family due to sudden behavioral changes. Over the past week, she has become increasingly paranoid, claiming people are watching her and whispering. She has auditory hallucinations, poor sleep, and emotional outbursts. Her family thought it was a psychiatric breakdown.
Two days before presentation, she developed slurred speech and abnormal jerky movements of her arms and face. She also had one generalized tonic-clonic seizure. There is no history of drug use or recent illness.
On examination:
- Disoriented to time
- Orofacial dyskinesias
- Tremulous, abnormal limb posturing
- No fever, no rash
- Vitals: Stable
- Fundus: Normal
- Reflexes: Brisk
Investigations:
- CBC, LFT, RFT, electrolytes: Normal
- Urine toxicology: Negative
- MRI Brain: Unremarkable
- EEG: Diffuse slowing
- CSF: Mild lymphocytic pleocytosis
- HSV PCR: Negative
- ANA: Negative
- What’s your leading differential, considering both psychiatric and neurological features?
- What specific antibody test would you order next?
- What condition could mimic psychosis in young women and requires urgent immunotherapy?