Christina and Brian Beck said their 14-year-old daughter was acting out of character and wouldn't even speak at one point. Doctors eventually learned her immune system was attacking her brain. The Becks said their daughter, Meredith, was a bright, straight-A student who did taekwondo and played the piano. But around December of 2018, they said she quickly started to act different."I mean, it was horrific. We didn't know what was happening," Christina Beck said.Christina Beck said her daughter first complained about not feeling like herself."And she said 'Well, I just... sometimes feel really scared and confused, and kind of like I'm going really crazy,'" Christina said.Meredith's parents and her pediatrician thought it may be anxiety.The 14-year-old saw a child psychologist and even took anxiety medications.But the Becks say Meredith's condition worsened. "She's starting to act lethargic, she started to say she was hearing voices," Christina said. "She would feel like someone was touching her back and no one was there."Within just days of seeing the pediatrician, the Becks say Meredith stopped sleeping and would throw up at least once a day."We had no idea what was happening and truly, the pediatrician didn't really know and the psychologist didn't know," Christina said.One day they got a call from Meredith's school."The counselor had found her at her locker, catatonic," Christina said. "Just turning the locker, wouldn't respond when the counselor called her name."After that, Meredith's parents took her out of school. The pediatrician suggested an EEG to check for seizures."So we took her to Children's. They did the EEG, it was totally normal," Christina said.At home, things weren't so normal.At times, Meredith became catatonic, not even moving or responding to her name."Just stood, in the room, arms by her side," Christina said. "Looked straight ahead, and I would say her name, she wouldn't respond."Doctors would test Meredith, but they didn't get anywhere with results.They finally decided to bring in a neurologist to get a closer look. "Immediately, when I saw her, I grew very concerned," said Dr. Mary Rickard, a pediatric neurologist. "They said, she's got a tumor the size of a deflated football on her left ovary and she's scheduled for surgery in the morning," Christina said.Doctors say her tumor looked like it had brain cells, causing Meredith's immune system to create antibodies that attacked her brain.Meredith's neurologist, Dr. Mary Rickard, diagnosed her with autoimmune encephalitis, also known as 'Brain on Fire.'"Unless you know what you're looking for, it's sometimes difficult," Rickard said.In Meredith's case, her immune system went after the NMDA receptor in her brain. "If it attacks NMDA, that's what the drug PCP works on. So think of a child acting like they're on PCP all day: That's what we're dealing with," Rickard told KETV Newswatch 7.Doctors removed Meredith's tumor, and treated her with steroids and a blood transfusion.Then, Meredith began rehab to get her speech and movement back."The neurologist told us that 12 years ago, our daughter would have been put in a psychiatric unit and she would've died there... because they didn't know as recently as 12 years ago, what was happening or how to stop it," Christina said.Within a month, she was back to her normal self.Rickard said this is because they acted quickly."Demand what you think is best for your child because it's a heartbreaking to us and the family if we delay care with these kids," Rickard said."We were so lucky, and we're so grateful that we got our daughter back and... lots of other families don't," Christina said.Now, Rickard says doctors are trying to find the best treatment for auto immune encephalitis. They also want to find out what exactly triggers the illness.