Doctors once told Carissa Resek’s parents she might never be able to walk – but the 31-year-old from Kaysville, Utah, has been proving them wrong ever since. Born with Apert syndrome, a rare genetic disorder that affects the shape of her skull, hands, feet, and facial structure, Resek has faced more medical challenges than most people will in a lifetime. Despite undergoing more than 40 major surgeries and enduring excruciating treatments like wearing a metal facial brace at age 6, Resek continues to live with recurring infections, sleep apnea, and other lasting impacts of her condition. Nevertheless, Resek has never let her diagnosis define her limits. Her resilience came into the spotlight when a video of her went viral. After unintentionally running 18 miles on her treadmill while watching a movie, she decided to keep going and completed a full marathon with family and friends cheering her on. “She never set out to run one,” her older brother, Erick Resek, tells PEOPLE exclusively. “After finishing a Harry Potter movie on her phone during a run, she realized she had already logged 18 miles on the treadmill.” After realizing she was already two-thirds of the way there, Carissa decided eight more miles wouldn’t hurt. She texted a few friends and family, and before long, they were by her side cheering her on. She finished all 26.2 miles in five hours and 31 minutes, powered only by mini muffins and tap water sipped through a straw. As a regular runner – often logging five to 10 miles a day – Carissa had completed a treadmill half-marathon before, but this was her first full one. “She loves watching movies while running, something she cannot do outdoors,” Erick says. “She’s raced a few local outdoor 5Ks, and you might spot her at a bigger event someday.” Given that the marathon was spontaneous, Carissa hadn’t consulted a doctor beforehand, but years of consistent running have kept her in excellent shape. Carissa was closely monitored in the days that followed, and luckily, she felt great. She even did her own laundry and vacuumed her room that same day – waking up the next morning without any soreness. “Now she says she wants to try again, with some more training and better shoes, and her goal is five hours and 15 minutes,” Erick reveals. Far from being held back by her condition, Carissa has become an inspiration – a reminder that strength isn’t about what you’re born with, but what you choose to do with it. “Carissa has never let her diagnosis slow her down,” Erick explains. “She graduated from high school, earned a culinary arts degree, and has been steadily employed since she was a teenager.” Today, Carissa cares for infants and toddlers at a local daycare, where the kids light up around her. She also helps in the kitchen, thanks to her food handler’s permit. A seasoned traveler, she’s explored Europe and spent three years living in Argentina while her parents were there on a church mission. Carissa has also completed her own service mission in Salt Lake City. Carissa, who is also fluent in Spanish, is known for memorizing movie lines, cooking, swimming – and now, thanks to her viral video, running with unstoppable determination. “Around the neighborhood, she is famous for the uplifting sidewalk-chalk messages she draws on the driveway, or showing up at your door with a fresh batch of cookies she baked from scratch,” Erick shares. Never miss a story — sign up for PEOPLE's free daily newsletter to stay up-to-date on the best of what PEOPLE has to offer​​, from celebrity news to compelling human interest stories. Living at home with her parents, Carissa is surrounded by family, friends, and neighbors who cherish her presence. Out of eight children, she is often labeled the favorite sibling. Carissa is also a deeply loved aunt, adored by her nieces and nephews. “Our parents and us siblings have always treated [Carissa] as an equal and encouraged every ambition,” Erick tells PEOPLE. “Sometimes she needs a nudge, like swimming with sharks, trying a zipline in Hawaii, or a roller coaster at Six Flags, but her own drive usually leads the way.”