When Chantelle Brown-Young was 4 years old, a mysterious white patch appeared on her stomach. Diagnosed with the skin disorder vitiligo, Brown-Young watched as similar spots spread all over her body over the next few years, including on her hands, knees and face.

“The bullying started when I went to school,” Brown-Young, 20, tells PEOPLE. “It was tough. I definitely had problems with self-esteem.”

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Although the cause of vitiligo is unknown, the disorder is believed to destroy cells that produce skin pigment, according to the National Institutes of Health. It causes white patches, which are more noticeable on naturally dark skin. In Brown-Young’s case, these patches are nearly symmetrical.

Her striking appearance caught the attention of Tyra Banks, who discovered Brown-Young on Instagram and asked her to compete in cycle 21 of America s Next Top Model, which premieres Aug. 18.

“I’d only been modeling for maybe a year before she found me, so I was pretty fresh,” says Brown-Young, of Toronto. “The fact that she wanted me so badly for her show will stick with me for the rest of my life.”

The self-proclaimed vitiligo spokesmodel hopes her run on the show will inspire others to follow their own dreams.

“Growing up, it was a ‘fake it ’til you make it’ type of thing. I just decided, You know what? I’m going to keep telling myself I’m beautiful until I feel beautiful.’ And it happened.”

America’s Next Top Model cycle 21 premieres Aug. 18 (9 p.m. ET) on the CW.

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