A 16-year-old high school student suddenly began seeing and hearing things that were not real. The most vivid vision was a flying green dinosaur. She also heard voices telling her to hurt herself and felt people were following her.
Parents first noticed changes weeks earlier. Her strong grades slipped and she pulled away from friends and activities. When the hallucinations started abruptly, she was taken to hospital.
Initial tests showed nothing wrong
Blood work, brain scans and basic checks all came back normal. Doctors treated her for possible psychiatric issues and gave medication for the ongoing psychosis. Still, her symptoms continued.
Rare diagnosis after weeks of searching
After nearly three weeks in hospital and many specialist visits, a special spinal fluid test finally gave the answer. It detected antibodies attacking a part of the brain’s support structure called the heavy-chain neuronal intermediate filament (anti-NIF).
This is a very uncommon form of autoimmune encephalitis where the immune system mistakenly attacks the brain.
Treatment and recovery
Doctors started immune-modulating treatments, managed infections that appeared and carefully checked for any hidden cancer (sometimes linked to this condition). The hallucinations and other symptoms slowly faded. She left hospital well and stayed stable on immunotherapy the following year without needing psychiatric drugs.
This case, published in early 2026 in “Clinical Practice and Cases in Emergency Medicine,” highlights how sudden psychiatric symptoms in a previously healthy teen can point to a treatable autoimmune brain disorder rather than a primary mental health problem.
Early recognition of such rare conditions can prevent long-term harm and lead to full recovery.
