Celine Dion stepped away from performing last year as she battled "stiff-person" syndrome, a rare neurological disorder that has affected her ability to walk and sing. Her sister, Claudette Dion, now says Dion doesn't have control of her muscles.

"There are some who have lost hope because that it is a disease that is not known," Claudette, 75, told French publication 7 Jours.

Claudette is also a singer and CEO and spokesperson for the Fondation Maman Dion, an organization founded by their mother that helps disadvantaged kids. 

"If you only knew how many calls we receive at the Foundation to hear from Céline," Claudette said in the French-language interview. "People tell us they love her and pray for her. She gets so many messages, gifts, blessed crucifixes. She works hard, but she has no control over her muscles. What makes me sad, is that she was also so disciplined."

Stiff-person syndrome, also called Moersch-Woltman syndrome, is a "rare neurological disorder with features of an autoimmune disease that causes the body to become rigid and more sensitive to noise, touch and emotional distress," according to the National Institute of Neurological Disorders and Stroke. It can also leave patients with "hunched over and stiffened" postures.

Dion opened up about her diagnosis in December 2022, saying she had to reschedule tour dates that had already been postponed due to the COVID-19 pandemic. In May 2023, she announced she was canceling the remaining dates of her world tour due to her health issues.

Claudette said their dream is for Dion to return to the stage, but it is uncertain. "Vocal cords are muscles, but so is the heart. That's what gets to me. Because it's one in a million case, scientists don't have that much research on the topic, because it didn't affect that many people."

Dion has had to postpone concert dates before. In 2014, she announced she was battling an illness that caused inflammation in her throat muscles and also had to care for her husband Rene, who had cancer. (He died in 2016.) Dion said in a statement at the time it had been "a very difficult and stressful" time for the family and she needed to postpone shows from her Caesars Palace residency and cancel Asia tour dates.

Stiff-person syndrome affects 1 in a million people, although some studies suggest that is an underestimate, according to the National Institutes of Health. The disease affects twice as many women as men and is often associated with other autoimmune diseases like Type 1 diabetes and vitiligo. Research suggests it could be caused by an autoimmune response in the brain and spinal cord gone awry, but the cause is not yet understood. 

Drugs that help alleviate muscle spasms as well as antianxiety drugs can help manage the disease and studies have shown that intravenous immunoglobulin treatment – IVs with natural antibodies donated by healthy people – can help reduce the stiffness.

In November, Dion, who is Canadian and had a long-running residency, made one of her few public appearances since her diagnosis, greeting members of the Montreal Canadiens NHL in Las Vegas.

In:
• Celine Dion

Caitlin O'Kane

Caitlin O'Kane is a digital content producer covering trending stories for CBS News and its good news brand, The Uplift.