A 16-year-old girl in California was referred to an emergency department after experiencing hallucinations, including a flying green dinosaur and voices urging her to harm others. She also felt she was being followed. Trembling, sweating, a racing pulse and rapid, shallow breathing prompted clinicians to investigate a possible physical cause. Although she described hallucinations stretching back about four years, her parents said they had noticed psychotic symptoms only during the preceding 48 hours.
A brain scan and a test of the brain's electrical activity offered no explanation. On her second hospital day, she entered a catatonic state, which subsided within days after treatment with lorazepam. A subsequent test of her cerebrospinal fluid detected autoantibodies targeting neuronal intermediate filament, a protein that provides structural support to nerve cells. She was diagnosed with autoimmune encephalitis, in which an immune attack on nervous tissue produces inflammation and can cause psychiatric symptoms. Scans looking for tumours, which can trigger the condition, found none.
Treatment included intravenous steroids, immunoglobulin from healthy donors and rituximab, which destroys antibody-producing B cells. She also underwent five sessions of plasma exchange over the following month to help remove harmful antibodies. Discharged after almost two months in hospital, she continued medication and monthly immunoglobulin treatments. As her symptoms improved over the following year, she stopped the psychiatric medicines olanzapine and lorazepam but remained on immune treatment. Autoimmune encephalitis is rare: a UK study estimated that it affects five to eight people per 100,000.
