Kids suffer from debilitating episodes after recovering from strep throat: Part 1

A once relaxed and positive child, Parker Barnes' parents say he suddenly developed odd tics, rage and anxiety, while Alexia Baier's parents said they feared for her and their family's safety.
9:00 | 07/21/18

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Transcript for Kids suffer from debilitating episodes after recovering from strep throat: Part 1
Get away! -- Is under attack. Mysteriououtbursts th look like metal illness. Hisarents, desperate for answers. It's okay, parker, we got you. Recordingse horrifying moments,ing that someone might know what's wng. And how to stop it. Behave yourself. No! Iant M boy these fits and att all suddenly staing after a bout of strep throat. We've known for a very long time that viruses can trigger mental ISS. Screaming. Reporter: Priorlake, Minnesota. Middle CSS middle America. It'sruising at the top. Yep. Repter: Parr Barnes is the oldestld in house full of activity. R kids, T do, we have a small business we both work besides that. Reporter:ectic life. Yeah. Rorter: His parents, Natalie and Ian, say their son is the kind of kid every parent dreamshaving. Parker, look here. Pr I affable,el he's G Ary stens of humor. He's veryive. Oh! ? You gotta be kidding me! I'm fisherman. Do U O the top bunk? Yea myickname th my mom and dad say he morphed somhing else. A year and a half ago WHE was, parker got strep throat. Within days strange symptoms appeared. He had a small throattick. It smoke he nevequ clearing his throat. It was MI Reporter: Parr took antibiotics and everything cleared up.t over theext three months, three rounds of strep. Parker, what are you talking about? Reporter: Each time myerious behaviors appeared and got worse. When H became socially anxiound shutimself what was your reaction? Thiss just -- this is ra Reporter: That P anxiety led to osive compulsive behave Don't do that, you're going to hurt yourself. Ror the normally, low-key boy with inexplicable rage. Son is in theidst of an behave yours N Reporter: Cry for he when parkerent his dad a text Messa Dad, I need you to com home no ran through the door, he's like, I T know I can't stopcrying, him horribly an I don't know W said, he's been kinda getting like this when he H store Reporter: Their doc commend seeing a psychologist.little didnyone know the real crisis was stillhead. You werabout to be blindsided? Ided likeou can never -- Never imagine. Reporter: One morning, parker and his ynger bro Stetson were getting ready for school. I said, go brush your teeth, the buss here in seven minutes. Let'et you O the door. He starts screaming, oh my god, per, what are you doing? He's got anife. Oh, god! I was the first oneo S What did you see? He H a knife. Hebout to literally S hi he's like, I'm useless. That's what he said, useless, I'm useless I grabbed the knife out just hugging him like, honehat is upityo is doesn't make sense to me. He's LI, I just didn't want me urt anybody with the strep anymore. E saidhat. He said that. I still didn't put it gather. I'm like, honey, it's just strep th. It's no big deal. Eporter: Wn WER your way to school and you picked U knife, do you remember that? Yes.I kin ofon't rememr a lot of it. Don't really like T think about it. Did you want hurt yourself? I don'teally know. It's like I 'T like the Sam it's like those two thoughts merged. Like they nd went in war. Anicked, Natalie and Brian called 911. Hours later, they had to do E unthinkable, admit their R- son to psychiatric hospital. Dropped H off. We left our son. A we don't get to stay. We don get T S And we had to lea. I just study children and try and understand ws wng with them how to help em. Reporter: Dr. Sue Swed works at the national inste mental he she bvesmon childod infections like stthtrigger Suen and drastic changes in some chiren like parker. O immune response, thatts the bra and gives rise T behavioral symptoms. Reporr: 400 miles away, just outside Chicago- family inri. Repr: Alexia got strep that for fwh sh was 4 years old. After treatment, her mom said sheha from a well happy chi to this -- Shut up! P, shut up how longntil you saw a change? Less than days later. It wasiance and OCD. Justeery. But it hits ornight? Yeeah. Just kept thinking, ws going on th M child? Reporter: Alexia was evened out of daycare after hing her classroom. Even she knows mething's won he would cry and say, mommy, wh can't I be good? I just want to good an you kn, that brokey heart. I'm going to kill you. When you're in the middle of a flare-up, can Y that something's happening? O. Not rally? T go and try to hurt people. The family came to a breaking point when alexia attd own mother. Ight up here. I pulled over. I turned to her and as I picked my head up, she W stabbing me in T eye with my mascara wand. All I could see out O it was black. Wasn't sure if it was -- did she bli me that eye, or is it the mascara. But it was violent enough? It was violent ou and itwas intentnal. T you hado put your 4-year-old in a psych ward? The hardest nine days of my life. Vanesays doctor sent her youngghter Hom W a number of pchiatric Dru used that schizophrenia and bipolar disorder. Did the drugs work? No. They made her like a shell of her person, and then she was still haviouts of ra a aggreson. Reporter: It took months befo a doctor finally connected Al's behavior to St A she said, no,ry single one of the symptoms that U're describing is a symptom of panda's. If you haven't heard paas, you not alone. Dr. Sw intified it more than twdecades ago. It stands for pediatric autoimmune neuro psyiatric disorders associated with strep infections. It affects 1 in 200 and in 500 every year. That's a huge numbe ch potentially. T is. She said those numbers act for a spectrum of cases ranging fro mor to severe, like alexia. Andt turns out, parker too. . Want to go F ak with the reporter: Dyoremember T in-patient hospital where you had T stay? Oh, that was a nightmare Ttas a nightmare? That was mikrison for child Great, good, pandas. Whatever pandasis. Is there ayrup for that? Whatever thatis, we'll be gone and Dow road. As you say, let's do it, start the Trent, let's fix this thing. Yeaut it wasn't that easy? No. Reporter: Next, inside crs-country journey to get pa hel How can you look at a child that isn this S and say, I'm sorry, I can't help Yo This is a ce

This transcript has been automatically generated and may not be 100% accurate.

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