LOS ANGELES (CBSLA.com) — Magnolia “Maggie” Tessler was your typical, spirited toddler.

She is the first child for AJ and Jenny Tessler.

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The proud parents captured all her milestones on camera. Attempted handstands in the living room, pretending to read the pages of her favorite bedtime story.

Her parents marveled at how quickly Maggie was growing.

But Jenny told KCAL9’s Kristine Lazar she also sensed something was wrong.

“We had been taking music class for like a year, and one day I went to sit down with Maggie, and they started the music and she just started screaming,” Jenny recalled.

First, they noticed odd behavior. Then Jenny noticed, slowly, Maggie started losing words.

“I was watching, and it was one word at a time which was going away and then finally one day I was like, she has completely stopped talking,” Jenny said.

AJ assured Jenny there was nothing to worry about.

“And my response was she is just working on other things,” AJ says.

Maggie’s pediatrician also told Jenny that her daughter was healthy.

“Nobody believed there was a problem. I would keep bringing up little things, but everything was minor. Our pediatrician would say ‘It will go away,’ ” Jenny says.

Instead, things got worse.

For months, Maggie’s parents waited for a diagnosis.

Finally, a blood test last December revealed what Maggie and the couple were up against.

“That was the one thing that stuck with me, the doctor said ‘at least you know what it is.’ And I did not want to know what it is,” says AJ.

Maggie was diagnosed with Rett Syndrome. It is a rare condition that affects mostly young women. Small hands and feet as well as smaller head growth; it’s often compounded with gastrointestinal disorders, a lack of verbal ability or the inability to walk.

There are other, equally terrifying symptoms.

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“Scoliosis, seizures, there are breathing abnormalities, even sudden death,” says Jenny.

Thus far, Maggie has maintained the ability to walk. She goes to physical and speech therapy five days a week, including horse therapy.

Her therapy is emotionally and physically draining.

“She is an amazing kid now, but we also have to fight so she is able to have the life she should be able to have,” says Jenny.

Last month, AJ and Jenny produced a YouTube video telling their daughter’s story. The video is ad-sponsored; the more times it is viewed, the more money it makes. All that money will be donated to Rett Syndrome research by Maggie’s parents.

“My goal for our video is to share our story, and in that way it has been cathartic. My hope for the video is that it will be seen by a lot of people and raise a lot of money for Rett Syndrome,” says AJ.

The video has more than 100,000 views.

“Someone sent me subtitles in German and subtitles in Portuguese, so we can share the video in those countries.”

Rett Syndrome is not hereditary. It could affect anyone.

Lazar also spoke to Larry Yin, who heads up the only Rett Syndrome clinic in Southern California at Children’s Hospital Los Angeles.

“Right now, the rates are 1-in-10,000 or 1-in-15,000, but the reality is we will see more cases of this because we are going to be looking for it more often because now we have a test,” says Yin.

There is hope for a cure. Lin says researchers have been able to reverse Rett Syndrome in mice.

“That is what gets us through the really hard times is going we have to stop this. This can’t happen to other people. We have to stop it for Maggie.”

The Tesslers no longer watch the home videos of a younger Maggie.

But they do continue to share her story on social media. They’re asking their friends and family — and their friends — to share the story, too.

“We need humanity to care; we need everybody to get behind this to save these girls,” says Jenny, fighting back tears.

Maggie will likely never be able to live on her own. But her parents will never give up hope. They’re trying to give their only daughter the life she deserves.

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“I know that I have told her that she needs to keep fighting because we are fighting for her,” says AJ.