Teenager's rare autoimmune disorder caused her to hallucinate a flying green dinosaur

The patient was a 16-year-old girl in California who experienced hallucinations, including seeing a flying green dinosaur and hearing voices instructing her to harm others. She exhibited trembling, sweating, a rapid pulse, and labored breathing in the emergency department. These hallucinations had been present for about four years, since seventh grade.

Initially, doctors suspected the hallucinations were due to a physical ailment, such as brain trauma, but a CT scan revealed no signs of swelling or hemorrhage in her head. After multiple failed attempts at cerebrospinal fluid testing, the girl entered a catatonic state, disrupting her ability to process and react to her surroundings.

She was treated with lorazepam and later transferred to a psychiatric ward after developing feeding difficulties. Psychiatrists prescribed the antipsychotic drug olanzapine. After eight days in the hospital, a subsequent cerebrospinal fluid test revealed autoantibodies targeting neuronal intermediate filament (NIF) protein, leading to the diagnosis of autoimmune encephalitis.

While a specific tumor was not found, the girl received intravenous infusions of steroids, immunoglobulin, and rituximab to reduce inflammation and eliminate autoantibodies. She also underwent plasmapheresis, a procedure that removes autoantibodies from the blood. After nearly two months in the hospital, the girl was discharged and continued to take olanzapine, lorazepam, prednisone, and monthly immunoglobulin treatments.

Her symptoms improved over the next year, and she eventually stopped taking psychiatric drugs but continued immunotherapy. Autoimmune encephalitis is rare, affecting only 5 to 8 out of every 100,000 people, with most cases targeting NMDA receptors. The girl's condition was not triggered by a specific infection, but her family reported she had been ill with a cough three weeks before seeking emergency care, and she had recently traveled to the Philippines where multiple family members contracted the same illness.