tonight -- >> sit down and behave yourself. >> -- children hijacked by a mysterious illness. >> i'm going to kill you. >> becoming angry, depressed and violent after a common infection. >> something came in and stole our child. >> families pushed to their limits. >> you had to put your 4-year-old in a psych ward. >> by a baffling disorder they don't know how to treat. >> they say, there's something wrong with my brain, can you fix it? >> inside the fight for answers to bring their children back from the brink? >> how can you look at a child in this state and say, i'm sorry, i can't help you? >> this special edition of

"nightline," mystery diagnosis, children under attack, will be right back. right back. (sound of footsteps) (sound of car door opening) (car door closes) (sound of engine starting) ♪ ♪

(sound of footsteps) (sound of car door opening) (car door closes) (sound of engine starting) ♪ ♪ this special edition of "nightline" -- mystery diagnosis, children under attack, continues. here joining us. tonight, you're about to meet families willing to share raw, often disturbing home videos of their children in full-blown crisis. stricken with a baffling

condition, seeming to rob their kids of their happiness and their sanity. we join these families searching for answers in our year-long examination of a disorder that's so often misunderstood. 12-year-old parker's brain -- >> get away! get away! >> -- is under attack. >> mysterious outbursts that look like mental illness. his parents, desperate for answers. >> it's okay, parker, we got you. >> recording these horrifying moments, hoping that someone might know what's wrong. and how to stop it. >> behave yourself. >> no! >> i want my boy back. >> these fits and attacks all suddenly starting after a bout of strep throat. >> we've known for a very long time that viruses can trigger mental illness. [ screaming ]. >> reporter: prior lake,

minnesota. middle class, middle america. >> it's cruising at the top. >> yep. >> reporter: parker barnes is the oldest child in a house full of activity. >> four kids, two dogs, we have a small business and we both work besides that. >> reporter: hectic life. >> yeah. >> reporter: his parents, natalie and brian, say their son is the kind of kid every parent dreams of having. >> parker, look here. >> parker is affable, relaxed. he's got a dry stens of humor. he's very positive. >> oh! >> what? >> you gotta be kidding me! i'm a fisherman. >> do you sleep up on the top bunk? >> yeah. my nickname that my mom and dad call me is lead dog. >> reporter: overnight they say he morphed into something else. a year and a half ago when he was ten, parker got strep throat. within days, strange symptoms appeared. >> he had a small throat tick.

it seemed like he never quit clearing his throat. it was minor. >> reporter: parker took antibiotics and everything cleared up. but over the next three months, three rounds of strep. >> parker, what are you talking about? >> reporter: each time, mysterious behaviors appeared and got worse. >> when he became socially anxious and shut himself off, what was your reaction? >> this is just -- this is strange. >> reporter: that paralyzing anxiety led to obsessive compulsive behavior. >> don't do that, you're going to hurt yourself. >> reporter: their normally, low-key boy with inexplicable rage. >> my son is in the midst of an absolute raging flare. >> you need to sit down and behave yourself. >> no! >> reporter: an urgent cry for help when parker sent his dad a text message. >> dad, i need you to come home now. i ran through the door, he's balling uncontrollably. i'm like, what is going on? he's like, i don't know, i can't

stop crying, him horribly sad and i don't know why. >> i said, he's been kinda getting like this when he has strep. >> reporter: their doctors recommend seeing a psychologist. little did anyone know the real crisis was still ahead. >> you were about to be blindsided? >> blindsided like you can never -- >> never imagine. >> reporter: one morning, parker and his younger brother stetson were getting ready for school. >> i said, go brush your teeth, the bus is here in seven minutes. let's get you out the door. he starts screaming, oh my god, parker, what are you doing? he's got a knife. oh, my god! >> i was the first one to see it. >> what did you see? >> he had a knife. he was about to literally stab him. he's like, i'm useless. that's what he said, i'm useless, i'm useless. >> i grabbed the knife out and i'm just hugging him like, honey, what is up with you? this doesn't make sense to me. he's like, i just didn't want me

to hurt anybody with the strep anymore. and he said that. >> he said that. >> i still didn't put it together. i'm like, honey, it's just strep throat. it's no big deal. >> reporter: when you were on your way to school and you picked up a knife, do you remember that? >> yes. i kind of don't remember a lot of it. i don't really like to think about it. >> did you want to hurt yourself? >> i don't really it's like i didn't but did. like the same. it's like those two thoughts merged. like they kinda went in war. >> panicked, natalie and brian called 911. just hours later, they had to do the unthinkable, admit their 10-year-old son to a psychiatric hospital. >> dropped him off. >> we left our son there. >> and we don't get to stay. >> we don't get to stay. >> and we had to leave. >> i just study children and try

and understand what's wrong with them and how to help them. >> reporter: dr. sue swedea works at the national institute of mental health. she believes common childhood infections like strep throat can trigger sudden and drastic changes in some children like parker. >> the wrong strep and the wrong kid results in the wrong kind of immune response, that impacts the brain and gives rise to behavioral symptoms. >> reporter: 400 miles away, just outside chicago -- another family in crisis. [ crying ]. >> reporter: alexia got strep throat for the first time when she was 4 years old. days after treatment, her mom said she changed from a well behav behaved happy child to this automat -- >> shut up! shut up, shut up! >> how long until you saw a

change? >> less than two days later. it was defiance and ocd. just seemed angry. >> but it hits overnight? >> yes, yeah. >> i just kept thinking, what's going on with my child? >> reporter: alexia was even kicked out of daycare after trashing her classroom. even she knows something's wrong. >> she would cry and say, mommy, why can't i be good? i just want to be good. and you know, that broke my heart. >> i'm going to kill you. >> when you're in the middle of a flare-up, can you sense that something's happening? >> no. >> not really? >> i just go and try to hurt people. >> the family came to a breaking point when alexia attacked her own mother. >> right up here. i pulled over. i turned to her and as i picked

my head up, she was stabbing me in the eye with my mascara wand. all i could see out of it was black. i wasn't sure if it was -- did she blind me in that eye, or is it the mascara. >> but it was violent enough? >> it was violent enough, and it was intentional. >> that you had to put your 4-year-old in a psych ward? >> the hardest nine days of my life. >> vanessa says doctors sent her young daughter home with a number of psychiatric drugs used to treat schizophrenia and bipolar disorder. did the drugs work? >> no. they made her like a shell of her person, and then she was still having bouts of rage and aggression. >> reporter: it took months before a doctor finally connected alexia's behavior to strep. >> and she said, no, every single one of the symptoms that you're describing is a symptom of panda's. >> if you haven't heard of pandas, you're not alone. dr. swedeo first identified it

more than two decades ago. it stands for pediatric autoimmune neuro psychiatric disorders associated with strep infections. >> it affects 1 in 200 and 1 in 500 every year. >> that's a huge number of children, potentially. >> it is. >> she said those numbers account for a spectrum of cases ranging from minor to severe, like alexia. and it turns out, parker too. >>. >> want to go for a walk with the dogs? >> reporter: do you remember the in-patient hospital where you had to stay overnight? >> oh, that was a nightmare. >> that was a nightmare? >> that was mike a prison for children. >> great, good, pandas. >> whatever pandas is. >> is there a syrup for that? whatever that is, we'll be gone and down the road. >> as you say, let's do it, start the treatment, let's fix this thing. >> yeah.

>> but it wasn't that easy? >> no. >> reporter: next, inside the cross-country journey to get parker help. >> how can you look at a child that is in this state and say, i'm sorry, i can't help you? this is a cell. so are all these. they work together, doing important stuff... like keeping your vital organs running and what not. the hitch? like you, your cells get hungry. feed them with centrum micronutrients. designed to nourish and revitalize you at the cellular level. restoring your awesome on the daily. centrum. feed your cells. on the daily. my gums are irritated. i don't have to worry about that, do i? actually, you do. harmful bacteria lurk just below the gum line. crest gum detoxify works below the gum line to neutralize harmful plaque bacteria and help reverse early gum damage. and, now there's new crest gum & enamel repair.

it gives you clinically proven healthier gums and helps repair and strengthen weakened enamel. gum detoxify and gum & enamel repair, from crest. gums are good, so is my check-up! crest. healthy, beautiful smiles for life. if your moderate to severe ulor crohn's symptoms are holding you back, and your current treatment hasn't worked well enough, it may be time for a change. ask your doctor about entyvio, the only biologic developed and approved just for uc and crohn's. entyvio works at the site of inflammation in the gi tract and is clinically proven to help many patients achieve both symptom relief and remission. infusion and serious allergic reactions can happen during or after treatment. entyvio may increase risk of infection, which can be serious. pml, a rare, serious, potentially fatal brain infection caused by a virus be pe. potentially fatal brain is cononot b infection caused by a virus reed withaveannfec experience frequent infections or have flu-like symptoms or sores.

liver problems can occur with entyvio. if your uc or crohn's treatment isn't working for you, ask your gastroenterologist about entyvio. entyvio. relief and remission within reach.

>> this special edition of "nightline" continues. >> parker, are you with us? >> no, he's not with us, honey. he's not here. >> 12-year-old parker barnes, and 4-year-old alexia baier, have been suffering debilitating episodes like these for months. >> get away!

get away! >> reporter: parker missed nearly a full grade of school and at one point stopped talking for four months. >> i would liken it mostly to an abduction. something came in the window and stole our child, but it's not our kid. our kid is gone. like, gone. >> after so much uncertainty, both families now have the same diagnosis, that disorder called pandas. some doctors believe pandas works like this. when anybody gets sick, the immune system makes antibodies to fight off the drugs, but those travel to the brain causing it to swell. they say that swelling can trigger a wide variety of neurological issues like ticks, rages, depression, or obsessive compulsive behavior. >> traditional onset ocd is gradual. comes over a period of days or weeks. pandas ocd comes on overnight.

it's lightning-like onset where the child is struck down. >> reporter: doctors say pandas is triggered by strep. pans is triggered by other common childhood illnesses like walking pneumonia, staph infections, even the flu. >> do you think that's our flight? >> reporter: on this day, parker and his mom are traveling more than 1,200 miles to washington, d.c. to see one of the few pandas specialists in the country. the wait list of desperate parents to see dr. elizabeth latimer can be months ago. >> dr. latimer, this is parker. >> can you say hi, parker? >> december is when he said he started having these mopies. >> did you ask him what that meant? >> just suddenly sad. >> reporter: in those heartbreaking videos of parker, dr. latimer recognizings the tell-tale signs of pandas. >> oh, he's got ticks, eye rolling. do you have worries?

do you have bad thoughts? >> yeah, i may have some bad thoughts occasionally. >> parker describes it as if his mind had been hijacked. >> yes. that's the most notable aspect of pandas compared to someone with true psychosis. these kids will come in and say, there's something wrong with my brain, can you fix it? >> can you take your shoes and socks off, please. >> reporter: although pandas often presents like a traditional illness, they believe the key is not just to treat the symptoms, but to focus on the overactive immune system. before seeing dr. latimer, parker had gone through a series of treatments, including antibiotics, steroids and infusions of healthy antibodies. but they only saw some improvement. >> it's very pricey. >> very pricey. >> reporter: any new treatments from lattimore would be more intensive and expensive.

but these treatments for pandas are rarely covered by insurance. >> i was like, do we sell the house? >> right. >> do we just live in an apartment? let's just sell it all. it doesn't matter. it's just stuff. >> reporter: but then natalie found another family had gotten one treatment covered, so her employer changed its policy it help parker. part of the difficulty getting coverage is thanks to the controversy surrounding the diagnosis. >> you're skeptical that pandas exists? >> yes. >> deeply skeptical? >> yes. >> dr. donald bill gert is a newer rolgs at cincinnati children's hospital. >> i think the majority of people who believe they have pandas just have ocd or ticks. >> reporter: he worked on early research study about pantas, but said there needs to be more data to prove that strep can cause these issues. >> you say you have patients referred to you who think they might have pandas. >> all the time. >> how often do you think those

are real? >> 1%. >> so you're saying it's overdiagnosed? >> way overdiagnosed, yes. the problem is, if you make a claim that the immune system is the culprit, it's going to harm them because you're going to hammer their immune system with a $10,000 treatment that they have no business getting. >> reporter: dr. swedeo and dr. latimer do point out many children develop psychiatric symptoms without infection. and many more kids get strep and never have behavioral problems. >> pandas is complicated. >> it's complicated, difficult, it's dirty, you're in the mud. people yelling at you, criticizing you. you gotta be able to take the slings and arrows. >> turn your hands up to the sky. >> reporter: they say the impact of the controversy on pandas research, education and treatment is huge. the american academy of pediatrics remains unconvinced, saying there is insufficient proof that strep causes these symptoms. its only treatment recommendation, send patients to a specialist.

although treatment guidelines were published in a different medical journal back in 2015. >> that's adorable. >> reporter: alexia's mom said all this medical infighting trickles down to them and their kids are suffering. >> after we find something that makes sense and still going to be met with skepticism and criticism and be told, no, i'm wrong, yet again, there's a lot of anger and hurt behind that. >> reporter: vanessa says, like many children treated for pandas, alexia start responding to antibiotics and other drugs. she also does behavioral therapy. she still has flares of ocd behavior when she's sick, but she's getting better. >> it's not a straight line recovery? >> that's the hard thing with pandas. it's not one size fits all. >> do you want to just go are? you done? >> reporter: a year and a half into his illness, parker is still struggling. >> bite down really hard. >> reporter: the trip to dr. latimer left natalie hopeful.

>> it will be okay. >> that's what i really want. >> reporter: but the family is still waiting to see if they can get that more advanced treatment she suggested. >> we're just one couple that represents thousands. probably tens of thousands. >> remember, it's not our story, it's our collective group's story. >> reporter: natalie and brian say they had been dismissed by too many doctors, instead forced to find help through an online community of parents just like them. >> what are your hopes for parker long-term? >> we expect to fight this through and find whatever it is, wherever it is, from whomever it comes from, that gives him the full recovery he deserves. how can you look at a child that is in this state and say, i'm sorry, i can't help you? get out your note pad. you call a friend. you get on the internet. you google something up. you figure it out. because asking the parents to do it is not right. you're a doctor. that's a sick child. both those things are abundantly clear. click in and do it.

i can't imagine how you sleep at night being a doctor and turning a child away that's sick like parker is. or worse. >> you're fighting to get that boy back? >> we're fighting to give him the opportunity to be the man we know he can be. >> we'll be right back. this special edition of "nightline" is sponsored by mercedes-benz. what about him? let's do it. ♪ come on. this summer, add a new member to the family. at the mercedes-benz summer event. lease the glc300 for $429 a month at your local mercedes-benz dealer. mercedes-benz. the best or nothing. stop fearing your alarm clock... with new*! zzzquil pure zzzs. a drug-free blend of botanicals with melatonin ...that supports your natural sleep cycle...

...so you can seize the morning. new! zzzquil pure zzzs. discover our largest variety of crab and crab dishes all year! like new crabfest combo. your one chance to have new jumbo snow crab with tender dungeness crab. or try crab lover's dream. sweet, juicy king crab and jumbo snow crab cozied up with crab linguini alfredo. even our shrimp is crab-topped! so hurry in and get your butter-dunkin' game on! 'cause crabfest will be gone in a snap. and now bring home the seafood you crave with red lobster to go. call or order online today. i knew at that exact moment ... i'm beating this. my main focus was to find a team of doctors. it's not just picking a surgeon, it's picking the care team and feeling secure in where you are. visit cancercenter.com/breast

thiswhatever size.le streaming tv for your family, it's saving money with flexible channel packs. live tv and the latest shows to stream. and all your streaming apps in one place... - even netflix. this is how xfinity makes life simple. easy. awesome. get started with xfinity internet and tv at a new low price, just $44.99 a month for 12 months. plus, ask about flexible channel packs. click, call or visit a store today.

♪ ♪ ♪ raindrops on roses and whiskers on kittens ♪ ♪ bright copper kettles and warm woolen mittens ♪ ♪ brown paper packages tied up with strings ♪ ♪ these are a few of my favorite things ♪ ♪ ♪

♪ >> our thanks to all the families who shared their experiences with us. you can find much more on their stories and information about pandas and pans online at abc news.com and our nightline facebook page. we hope you join the conversation. goodnight, america. have a great weekend. at weekend.

i'm ready. but, clearly, i'm a little nervous. there are so many expectations. like, on the sticker, "city mileage this, highway that." uh, that's a lot to live up to. but i heard no gas gets better mileage than chevron with techron. yeah, no better mileage. it's proven. so that's a confidence builder. it's proven; no gas gets better mileage than chevron with techron. care for your car. so much for my new car smell, guys.