Lizzie Velasquez arrives at the premiere of “A Brave Heart: The Lizzie Velasquez Story” at Paramount Theatre on March 14 in Austin. (Michael Buckner/Getty Images for SXSW)

A 26-year-old Texan, Lizzie Velasquez stands 5 feet 2 inches tall. She weighs a little more than 60 pounds. That’s because she suffers from a rare syndrome that keeps her from gaining weight. Throughout her life, her condition has made her a target for bullies, who once dubbed her the “world’s ugliest woman” on social media. But over the years, she said, she has used others’ negativity to “light my fire to keep me going.”

Velasquez shared her story in a documentary called “A Brave Heart: The Lizzie Velasquez Story,” which premiered on Saturday at the South by Southwest music and film festival in Austin.

“It’s a movie with my face,” she told the Austin Chronicle. “But it’s not just me. It’s everyone.”

Velasquez is a motivational speaker who uses her experiences to fight bullying.

Velasquez was born eight weeks premature, weighing only two pounds. Doctors told her parents she might never crawl, walk or talk. They didn’t know how long she would live. Today, she is blind in one eye and visually impaired in the other. She has undergone numerous surgeries on her eyes and ears as well as a foot reconstruction, BBC News reported. It wasn’t until recently that doctors even gave her condition a name. She has two: Marfan syndrome, which affects her body’s connective tissue, and lipodystrophy, which makes it difficult to put on weight. Only two other people in the world are known to have it, she said.

Despite Velasquez’s differences, she said, as a child she thought she was normal.

“When I started kindergarten, I had no idea I looked different. I think of it as a big slap of reality for a 5-year-old,” she said during a TED Talk in 2013. She said she walked up to a little girl and “she looked up to me like I was a monster.”

“My first reaction was that she was really rude,” she said.

Velasquez was bullied throughout her childhood, she said, but it wasn’t until high school that it became unbearable — and inspired her to make a change.

“We did have obstacles with pointing and staring, but it was just kind of like we dealt with it, and we just got used to it,” her sister, Marina Velasquez, told Fox News in Austin. “It was normal.”

That changed one afternoon in 2007 when Velasquez, then 17, was surfing the Internet, avoiding homework. She said she went online to look for music videos on YouTube and that’s when she saw it: a YouTube clip called “The Ugliest Woman In The World.” It was a video about her — and it was viewed more than 4 million times.

“I don’t even know why I clicked on it,” she said in the trailer for her documentary. “But I did and that’s when I lost it. Calling me a monster or asking me why my parents didn’t abort me. ‘Kill it with fire. I wish you were dead. Just pick up a gun and end my life.’ ”

“How in the world can I forgive the people who told me to kill myself?” she said.

Velasquez decided to act. She created a Web site. She started a YouTube channel, which has more than 300,000 subscribers. She gave a TED Talk in 2013 at the TEDxAustinWomen in Austin. The video of it has more than 7 million views.

“I’m not sure what it was about the TED Talk or what I said in it, but it changed everything,” she told USA Today. “I knew this is my purpose. This is what I’m meant to do for the rest of my life because I like to think that I’m not only telling my story, I’m telling everyone’s story.”

This documentary follows the inspiring journey of 26-year-old anti-bullying activist Lizzie Velasquez, who suffers from a rare syndrome that keeps her from gaining weight. (The Lizzie Project via YouTube)

It was a defining moment. Months later, she started shooting a documentary to chronicle her journey. It premiered over the weekend. The film’s director, Sara Hirsh Bordo, told BBC News that the story is for anyone who has been victimized by bullies.

“Her experience of triumphing adversity and making it to the other side of a painful experience is universal,” she said. “As soon as Lizzie became more open and honest — whether it was her TED Talk or her YouTube videos — it was clear that people were thirsty for a story where somebody stands up and says, ‘I’m not going to be a victim; I’m going to make a change.’ ”

Velasquez said she did it and hopes other will, too.

“I don’t want people to feel sorry for me. At all,” she told the Austin Chronicle. “I want them to leave [the film] and feel empowered for themselves and, hopefully, for other people.”