Teen’s Hallucinations Were Linked to Rare Autoimmune Encephalitis

A 16-year-old girl in California who saw green dinosaurs flying, heard voices telling her to hurt others and felt that she was being followed was ultimately diagnosed with a rare form of autoimmune encephalitis.

Doctors discovered that antibodies in her blood were attacking a protein that helps support nerve cells. The unusual case highlights how autoimmune encephalitis can sometimes resemble a psychiatric illness.

Hallucinations and Abnormal Vital Signs

The teenager went to the emergency room after experiencing vivid hallucinations and other troubling symptoms. During a conversation with an emergency-room clinician, she responded to the dinosaur she saw as if it were physically present in the room.

She told doctors that the hallucinations had been occurring since seventh grade, or for about four years. Her parents said she had not displayed psychotic symptoms during the 48 hours before her hospital visit, although she had become less interested in school and extracurricular activities during the previous month.

At the emergency room, the girl was shivering and sweating. Her pulse was rapid, and her breathing was shallow and fast. She did not initially have a fever, but developed one after being transferred to the hospital.

Initial Tests Did Not Reveal the Cause

Because the teenager’s vital signs were abnormal, doctors suspected that an underlying physical illness could be causing her hallucinations. Potential causes included trauma to the brain.

A CT scan showed no swelling or bleeding in her head. Doctors attempted a lumbar puncture, also known as a spinal tap, but were initially unable to collect cerebrospinal fluid for testing.

Because she was medically unstable, doctors decided that she should not yet be transferred to a psychiatric ward. Instead, she was admitted to a general pediatric unit. A pediatric neurologist ordered an electroencephalogram, or EEG, which measures electrical activity in the brain, but the test did not provide further clues.

A Sudden Recovery Raised More Questions

On the second day of hospitalization, the girl made a complete recovery from a nervous state known as catatonia. Catatonia can affect how a person processes and responds to the world, and people experiencing it may stop moving or speaking.

Doctors treated her with lorazepam, a medication used to treat catatonia. Her slowed nervous-system signaling improved, and the catatonia subsided within a few days.

An interventional radiologist later performed a second lumbar puncture successfully. The first panel of cerebrospinal-fluid tests appeared normal.

After eight days in the hospital, a psychiatrist recommended transferring the girl to a psychiatric ward. However, she was still having difficulty eating independently, so the transfer was not possible. Her ongoing psychotic symptoms were treated with the antipsychotic medication olanzapine.

Doctors Identified Autoimmune Encephalitis

Although the initial cerebrospinal-fluid tests showed no evidence of meningitis or other abnormalities, a later test detected autoantibodies. These are immune proteins that mistakenly target healthy tissue instead of foreign invaders.

The antibodies targeted neuronal intermediate filament, or NIF, a protein that provides structural support to nerve cells. Based on this finding, doctors diagnosed the teenager with autoimmune encephalitis.

Autoimmune encephalitis occurs when the immune system attacks nervous tissue. The resulting inflammation can cause neurological and psychiatric symptoms, including hallucinations, confusion and changes in behavior.

Autoimmune encephalitis is sometimes associated with a tumor. Proteins produced by a tumor can resemble proteins in nerve tissue, prompting the immune system to attack healthy neurons. In this case, MRI and PET scans found no tumor.

Treatment Included Immunotherapy

The girl received steroid infusions to reduce inflammation and immunoglobulin, which consists of antibodies from healthy donors and is often used to calm autoimmune reactions.

She also received rituximab, a medication that destroys B lymphocytes. These white blood cells produce antibodies, including the antibodies attacking the girl’s neurons.

In addition, she received five injections of plasma exchange therapy over the following month. During plasma exchange, blood is removed from the body, a machine separates the plasma from the blood cells, and the plasma is replaced with a replacement fluid before the blood is returned. The procedure helps remove autoantibodies from the bloodstream.

The girl was discharged after spending about two months in the hospital. She continued taking prednisone, monthly immune globulin, olanzapine and lorazepam. As her symptoms improved over the following year, she stopped taking the psychiatric medications but continued immunotherapy.

Why This Case Was Unusual

Autoimmune encephalitis is rare. One study conducted in the United Kingdom estimated that it affects approximately 5 to 8 people per 100,000.

Most information about autoimmune encephalitis in children comes from cases involving antibodies that target the NMDA receptor, which detects the brain’s primary chemical messenger. In this case, the antibodies targeted NIF instead.

The case report did not identify a specific trigger for the girl’s illness. However, her family reported that she had been coughing for three weeks before she went to the emergency room. The family had been visiting the Philippines, where the girl and several relatives contracted the same illness.

The doctors did not diagnose the teenager with a specific infection. Anti-NIF autoimmune encephalitis has also been reported in adults and has been associated in some cases with tick-borne bacterial infections, HIV and COVID-19. Cases linked to these infections are rarer than those associated with tumors.

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