In a five-minute video, the Dion, 54, said the incurable condition affects about one in a million people. Fewer than 5,000 people in the U.S. are estimated to have the syndrome.
"While we're still learning about this rare condition, we now know that this is what's been causing all of the spasms I've been having," the singer said.
According to the National Institute of Neurological Disorders and Stroke, the condition is characterized by muscles that tense uncontrollably, and a heightened sensitivity to stimuli such as noise, touch and emotional distress, which can set off muscle spasms.
"Unfortunately these spasms affect every aspect of my daily life," Dion said. "Sometimes causing difficulty when I walk and not allowing me to use my vocal chords to sing the way I'm used to."
Because those with the disease can't control their bodies effectively, they're more prone to falling and injuring themselves because they can't move to catch themselves, according to NINDS.
Because of this, Dion said she wouldn't be able to continue her already-rescheduled European tour, which was set to begin in February 2023.
As it worsens, the condition ultimately leaves sufferers as "human statues" who are unable to walk or talk as the disease locks their bodies into rigid positions for hours at a time.
While there is no cure for stiff-person syndrome, it can be treated with muscle relaxants, anti-convulsants and other drugs.
"With appropriate treatment, the symptoms are usually well controlled," according to the NINDS website.
Dion said she was receiving medical treatment to slow the progression of the disease.
SPS affects twice as many women as men.
It is frequently associated with other autoimmune diseases such as type-I diabetes, thyroiditis, vitiligo, and pernicious anemia, NINDS said.
Scientists don’t yet understand what causes SPS, but research indicates that it is the result of an autoimmune response gone awry in the brain and spinal cord.