A 16-year-old girl in California began experiencing something that sounded almost impossible: she could see a flying green dinosaur that nobody else could see.
But the bizarre hallucination was only the beginning.
The teenager also heard frightening voices, believed people were following her, and began behaving in ways that deeply concerned her family.
At first, her symptoms appeared to suggest a serious psychiatric disorder. However, doctors soon discovered that something far more unusual was happening inside her body.
Her immune system was mistakenly targeting her own nervous system, causing a rare form of brain inflammation known as autoimmune encephalitis.
The remarkable medical case, described by physicians at Loma Linda University Medical Center and highlighted in October 2026, reveals how an autoimmune disease can sometimes produce symptoms that closely resemble severe mental illness.
A Flying Dinosaur That Seemed Completely Real
According to the published medical case report, the previously healthy teenager was brought to an emergency department after developing alarming visual and auditory hallucinations.
One of her most unusual experiences involved seeing a flying green dinosaur.
This was not simply an imaginary creature she described to doctors. During her medical examination, she appeared to react to the dinosaur as though it were physically present in the room.
She also reported hearing voices telling her to harm herself and feeling convinced that someone was following her.
Interestingly, the teenager told doctors that her hallucinations had started when she was in seventh grade, approximately four years earlier.
Her parents, however, reported that they had not noticed psychotic symptoms until roughly 48 hours before her hospitalization.
They had observed other concerning changes during the preceding month.
Her previously excellent academic performance had begun to decline, and she seemed less interested in social activities and extracurricular interests.
These changes initially appeared subtle, but they would eventually become important pieces of a complicated medical puzzle.
Doctors Noticed Something That Didn’t Fit
When the teenager arrived at the hospital, doctors discovered that her symptoms extended beyond hallucinations and unusual behavior.
She was experiencing several physical abnormalities, including:
- A persistently rapid heartbeat
- Excessive sweating
- Trembling
- Rapid, shallow breathing
- A recent episode of fever
- Sudden behavioral and psychological changes
Her heart rate was recorded at approximately 140 beats per minute, significantly faster than expected for someone resting.
These findings raised concerns that an underlying physical illness might be responsible for her psychiatric symptoms.
Doctors ordered laboratory tests and brain imaging to investigate possible causes.
A CT scan revealed no obvious brain bleeding or swelling.
Additional examinations, including an electroencephalogram (EEG), failed to identify a clear explanation.
Despite these initially reassuring findings, the medical team remained concerned.
The teenager’s abnormal vital signs and rapidly progressing symptoms suggested that something more than a primary psychiatric condition might be involved.
Her Condition Suddenly Became Much Worse
On her second day in the hospital, the teenager developed another serious complication.
She entered a state known as catatonia.
Catatonia is a neurological and behavioral syndrome that can severely affect movement, speech, and responsiveness.
People experiencing catatonia may become unusually still, stop speaking, or struggle to respond to their surroundings.
The medical team treated her with lorazepam, a medication commonly used to manage catatonic symptoms.
Over the following days, her condition improved somewhat, but her hallucinations and other problems persisted.
Doctors continued investigating.
A subsequent lumbar puncture allowed them to examine cerebrospinal fluid, the protective liquid surrounding the brain and spinal cord.
Early testing did not identify an obvious infection or another clear explanation.
For a time, the cause remained a mystery.
Then, a specialized laboratory test revealed the crucial clue.
The Surprising Diagnosis: Her Immune System Was Attacking Her Nervous System
On approximately the 18th day of hospitalization, doctors received results showing that the girl’s cerebrospinal fluid contained unusual antibodies.
These antibodies targeted a structure called the neuronal intermediate filament, or NIF.
Normally, antibodies help the immune system recognize and fight infections.
However, in autoimmune diseases, certain antibodies mistakenly recognize parts of the body’s own tissues as targets.
In this case, the findings supported a diagnosis of anti-NIF autoimmune encephalitis, an exceptionally uncommon form of immune-mediated neurological disease.
Autoimmune encephalitis occurs when the immune system attacks components of the brain, leading to inflammation and disruption of normal neurological function.
Depending on which brain structures are affected, symptoms may include memory problems, confusion, seizures, personality changes, movement abnormalities, and psychiatric disturbances.
For this teenager, the condition manifested through vivid hallucinations, behavioral changes, and catatonia.
Her case illustrates an important medical reality: not every psychiatric-looking symptom originates from a primary psychiatric disorder.
Sometimes, the underlying problem is neurological, infectious, metabolic, or autoimmune.
What Causes Autoimmune Encephalitis?
Autoimmune encephalitis is not a single disease but a group of conditions involving immune responses directed against the nervous system.
Researchers have identified multiple antibodies associated with different forms of the disorder.
One of the better-known varieties involves antibodies against NMDA receptors, proteins that play an important role in communication between brain cells.
The teenager’s condition was different.
Her antibodies targeted neuronal intermediate filaments, structural proteins that help support nerve cells.
This form is particularly rare in children and adolescents.
Certain cases of autoimmune encephalitis are associated with tumors, which can trigger an immune response that mistakenly recognizes proteins within the nervous system.
Other cases may develop following infections, although establishing a direct trigger is often difficult.
In the California teenager’s case, doctors performed additional imaging to investigate whether an underlying tumor might be involved.
The scans did not reveal cancer.
Her family also reported that she had developed a respiratory illness after traveling to the Philippines several weeks before hospitalization.
However, doctors did not establish that this illness caused her autoimmune condition.
The precise trigger remained unknown.
The Treatment That Helped Her Recover
Once doctors identified the autoimmune disorder, treatment focused on reducing inflammation and controlling the abnormal immune response.
The teenager received several specialized therapies.
1. High-dose corticosteroids
Doctors administered intravenous steroids to suppress inflammation and reduce harmful immune activity.
2. Intravenous immunoglobulin (IVIG)
This treatment involves administering concentrated antibodies collected from healthy donors.
IVIG can help regulate abnormal immune responses in certain autoimmune neurological conditions.
3. Rituximab
The teenager also received rituximab, a medication that targets B cells, which are involved in antibody production.
The treatment was intended to reduce the immune activity contributing to her illness.
4. Plasma exchange
She underwent five sessions of plasmapheresis, also called plasma exchange.
During this medical procedure, plasma is separated from blood cells and replaced with a substitute fluid.
The process can help remove circulating antibodies involved in autoimmune disease.
These were hospital-based treatments requiring specialist supervision, not home remedies.
After nearly two months in the hospital, the teenager was finally discharged.
Her recovery continued over the following year.
According to the case report, her psychiatric symptoms eventually resolved sufficiently for doctors to discontinue her psychiatric medications.
However, she continued receiving immune-directed therapy.
Her improvement demonstrated that even severe neurological symptoms associated with autoimmune encephalitis can respond to appropriate treatment.
Seven Warning Signs of Autoimmune Encephalitis
Although autoimmune encephalitis is rare, recognizing possible warning signs can be important.
Symptoms vary considerably between patients, but clinicians may investigate the condition when several of the following features occur together.
1. Sudden personality or behavioral changes
Someone may develop unusual behavior, agitation, paranoia, or dramatic personality changes over days or weeks.
2. New hallucinations or delusions
A person may begin seeing or hearing things that are not present or develop strongly held beliefs that do not match reality.
3. Unexplained memory problems
Short-term memory loss, confusion, or difficulty concentrating may develop unexpectedly.
4. Seizures
Some patients experience new seizures, including episodes that may initially be mistaken for other conditions.
5. Unusual movements or catatonia
Abnormal movements, significant stiffness, reduced responsiveness, or difficulty speaking may occur.
6. Disturbances in heart rate, temperature, or breathing
Some forms of autoimmune encephalitis affect the autonomic nervous system, potentially causing rapid heart rate, excessive sweating, or unstable body temperature.
7. Rapidly worsening neurological or psychiatric symptoms
A combination of psychiatric symptoms and neurological abnormalities developing over a short period deserves prompt medical evaluation.
Importantly, these symptoms are not specific to autoimmune encephalitis. Many other medical and psychiatric conditions can produce similar problems, and autoimmune encephalitis remains an uncommon explanation.
Sudden confusion, seizures, altered consciousness, or hallucinations accompanied by serious physical symptoms require urgent medical attention.
Why Normal Brain Scans Don’t Always Rule It Out
One particularly surprising aspect of this case was that several early examinations failed to identify a clear abnormality.
The teenager’s initial CT scan did not show obvious damage, and her EEG did not explain her symptoms.
Even her routine cerebrospinal fluid studies were initially unrevealing.
This is important because autoimmune encephalitis does not always produce obvious abnormalities on standard imaging.
Depending on the type of disease and its stage, MRI findings may be normal or nonspecific.
In some patients, specialized antibody testing and careful clinical assessment become essential to establishing the diagnosis.
However, antibody results must be interpreted alongside symptoms and other investigations. A laboratory finding alone does not always prove that antibodies are causing a person’s illness.
The California case demonstrates why physicians sometimes need to continue investigating when the overall clinical picture remains concerning despite normal initial tests.
Could Autoimmune Encephalitis Be Mistaken for a Mental Health Disorder?
Yes, and this is one of the challenges surrounding the condition.
Autoimmune encephalitis can sometimes begin with symptoms that resemble psychiatric disorders, including psychosis, severe mood changes, or behavioral disturbances.
However, this does not mean that psychiatric diagnoses are generally caused by autoimmune disease.
Most people experiencing hallucinations or psychiatric symptoms do not have autoimmune encephalitis.
Doctors become more suspicious of an underlying neurological or autoimmune condition when psychiatric symptoms occur alongside findings such as seizures, unusual movements, fluctuating consciousness, fever, marked autonomic instability, or rapid cognitive decline.
In the teenager’s case, her rapid heartbeat, abnormal breathing, sweating, and eventual catatonia helped indicate that further medical investigation was necessary.
The goal is not to dismiss psychiatric disorders, but to recognize when additional neurological evaluation may be appropriate.
A Rare Case With an Important Medical Lesson
The California teenager’s experience sounds almost fictional.
A young girl sees a flying green dinosaur, hears frightening voices, and begins behaving in ways that nobody around her can explain.
Yet behind those extraordinary symptoms was a real neurological illness.
Her immune system was mistakenly targeting structures within her nervous system, producing a rare inflammatory condition that dramatically affected her behavior and perception.
After extensive testing and specialized treatment, she experienced substantial improvement.
The case also emphasizes why unusual psychiatric symptoms accompanied by neurological or systemic warning signs should not automatically be attributed to a primary mental health disorder.
Sometimes, the most unusual symptom is only the visible sign of a much more complicated medical problem.
And for this teenager, identifying that hidden problem changed the course of her treatment.
