Imagine a neurologic disease that mimics what it feels like to inexplicably lose your mind.

One minute, you’re a healthy young woman whose biggest concern is acing a test in your college chemistry class. Suddenly, you start having hallucinations and delusions. Then, you progress to seizures and catatonia, which can mean you’re awake but don’t respond to anything or anyone, the US National Library of Medicine (NLM) says.

Finally, you slip into a coma and don’t wake up until weeks or months go by.

That is what autoimmune encephalitis (AE) can do to you. The disorder is a form of traditional encephalitis, an inflammation of brain, says the NLM.

Traditional encephalitis is caused by a virus or bacteria, the NLM says. But autoimmune encephalitis occurs when the body’s immune system unexpectedly creates antibodies to attack the brain, says Eric Lancaster, MD, PhD, an Assistant Professor of Neurology at Penn Neuroscience Center.

Autoimmune encephalitis: A rare, frequently misdiagnosed disorder

It’s worth remembering that AE is very unusual Dr. Lancaster says.

“There are hundreds of patients with other causes of psychosis for each patient with anti-NMDAR encephalitis,” he says. “Everyone with these more common conditions (such as schizophrenia) should not think that they have the antibodies that are linked with AE.”

The good news is that once people are correctly diagnosed with AE, the correct treatment can often make it possible for them to get back to work, school, or other daily life.

The bad news is because the disorder is rare and can even mirror psychiatric illnesses, getting that right diagnosis can be a long, frustrating journey, Dr. Lancaster says.

“The first step is getting a neurologist or psychiatrist to recognize that this might be what’s going on with this young person, who suddenly has behavioral change and some possible symptoms of psychosis,” says Dr. Lancaster.

There’s not a good estimate of how many people have autoimmune encephalitis in the US. Yet, the Autoimmune Encephalitis Alliance (AEA) says the disorder is likely more common than people might realize.

It is now known that there are at least 13 different types of autoimmune encephalitis, the AEA says. The most common type affecting young people—known as anti-NMDA receptor encephalitis—was first identified in 2007 by Josep Dalmau, MD, PhD, and his colleagues at Penn Medicine.

Anti-NMDA receptor encephalitis develops because the immune system has created antibodies that specifically attack the NMDA receptors in the brain.

“These antibodies will very selectively mess up an important neurotransmitter system in the brain, and it disrupts what that receptor’s normal functions were,” explains Dr. Lancaster.

Those functions include controlling rhythm in your breathing and movement, and allowing you to learn new ideas and store memories in your brain.

Many of the other known types of autoimmune encephalitis were also discovered by Penn Medicine, thanks to research done by Dr. Dalmau, notes Dr. Lancaster. And Penn Medicine remains one of the few centers around the country that specializes in these immune-mediated neurologic disorders, he notes.

Who is at risk

Most people who develop anti-NMDA receptor encephalitis are young women. The average age is 20.

However, Dr. Lancaster says various forms of AE affect both genders as well as people of different ages. The different types of AE also bring with them different risks for developing various types of cancer, which complicates the condition.

“You have to take into account that some of them have tumors, and not miss them. Then, you need to coordinate what you’re doing with the care of cancer,” says Dr. Lancaster.

Often first discovered in a psychiatric hospital

Because the behavioral change in people can be quite dramatic, Dr. Lancaster says it’s not unusual for these people to be checked into a psychiatric hospital first.

“It might be thought that the young woman has symptoms of schizophrenia or some other psychiatric illness,” he explains.

Bizarre behavior and speech, delusions, hallucinations—all can be symptoms of schizophrenia or AE, says Dr. Lancaster. Usually, it’s when neurological symptoms appear—-like seizures or a lack of responsiveness—that physicians realize the problem is not psychiatric.

Yet, to say the least, this uncertainty about the real cause behind their loved one’s illness—and a lot of misdiagnosis by doctors who have never heard of AE—can be unbelievably frustrating for the families of patients.

“It’s very tough for the families,”  Dr. Lancaster says. “The patients are often so impaired cognitively (with their thinking) that they’re not suffering as much as the family is.”

“Brain on fire”

That was the case with Susannah Cahalan, who was 24 when she suddenly developed AE. Susannah famously wrote about her experience in the best-selling book, “Brain on Fire: A Month Of Madness.”

Susannah progressed from violence to catatonia, she says in her book. Despite $1 million worth of blood tests and brain scans, it wasn’t until a physician thought to test for autoimmune encephalitis that she got a correct diagnosis. Susannah is now a reporter at the New York Post.

A long road ahead

When a doctor suspects that a patient has AE, a variety of tests are needed to verify that. For instance, neurologists usually do a lumbar puncture, drawing a small amount of spinal fluid out of the spine. Doctors test it for specific antibodies that allow them to diagnose the disease,” Dr. Lancaster explains.

“There’s a lot of work to get the diagnosis right and then treat the patient,” Dr. Lancaster says. “When your patient is in the ICU because of his symptoms, you’re doing a tremendous job keeping that patient alive. Then, you’re working for weeks and sometimes years thereafter to keep the patient healthy.”

Treatment has to be customized for each patient, whether that’s steroids, chemotherapy, or some other avenue, he adds.

“One of the big things is just being willing to escalate treatments appropriately, if the first line of treatment doesn’t work,” he says. “It can really take months before a patient starts to turn around.”

And the outcome for each patient is different.

“With these diseases, there’s always a risk that the patient could die,” Dr. Lancaster says. About 6% of people with anti-NMDA receptor encephalitis lose their lives.

Other forms of autoimmune encephalitis can be even more dangerous because they’re linked to deadlier cancers or don’t respond as well to treatment, he says.

“With a lot of my patients who have recovered, you can have a conversation with them on the bus and you would not know that anything had happened to them,” he says. “Probably a lot of them are like that.”

“That’s part of the reason why it matters so much to get the diagnosis right—to push people as hard as you can in the right direction.”

Watch Amanda's story and learn how she came to Penn for her rare autoimmune diease