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Two months before the treatment that would change Lynn Montgomery-Haga’s life, she could barely walk down a hallway.

In a test at the University of Colorado Anschutz, Montgomery-Haga struggled to walk 25 feet, often reaching out to the walls for support. Usually, the 49-year-old relied on her walker or wheelchair. “She had a very stiff, hesitant gait,” says Montgomery-Haga’s neurologist, Amanda Piquet.

For about a decade, Montgomery-Haga had lived with a debilitating autoimmune disease known as stiff person syndrome. The progressive condition can lock up the body’s muscles without warning, leading to falls, broken bones, excruciating pain and difficulty moving. Singer Celine Dion, who returned to the stage in September after years of battling the disease, has said it can feel “like somebody’s strangling you.”

Montgomery-Haga’s own days were marked by dizziness, fatigue and pain.…