Celine Dion's sister says the Grammy Award-winning singer is facing further challenges as she continues to live with a rare neurological disorder.

Claudette Dion said in a new interview that her sister is focused on overcoming her illness, called stiff person syndrome, but that progress has been difficult.

“She is working hard, but she does not have control of her muscles,” the elder sister told Quebec news outlet 7 Jours in an interview translated from French.

“Vocal cords are muscles, and the heart is also a muscle. That is what really hits me.”

She said the illness affects an estimated one out of a million people and is not yet well understood by current medical science.

Representatives for the Quebec-born songstress did not immediately respond to requests for comment.

The 55-year-old announced last December that she had been diagnosed with the rare neurological disorder which leads to muscle rigidity and spasms that can be very painful.

The spasms can cause people to fall and put them at risk of injury. If the thoracic muscles are affected, people can have difficulty breathing.

Dion was determined to persevere, first delaying a block of dates on her “Courage” world tour, but by last May, she was forced to cancel the remaining dates through April 2024.

“I'm not giving up... and I can't wait to see you again,” she said in May.

Her 75-year-old sister said fans of the “My Heart Will Go On” singer continue to send messages of support through the Fondation Maman Dion, the charity created in their mother's name to support grade schoolchildren.

“People tell us they love her and they are praying for her,” she said.

“She is receiving so many messages, gifts, blessed crucifixes.”

She added: “What pains me is that she has always been disciplined. She has always worked hard.

“Maman always told her: 'You are going to do it well, you are going to do it properly.' Definitely, in our dream and in hers, the idea is to return to stage. In what state? I don't know.”

Dion's sister, who is also a well-known Quebec singer, has offered updates on her condition in recent months, including one to Hello! Canada over the summer where she said the spasms “are impossible to control.”

“There's little we can do to support her, to alleviate her pain,” she told the publication.

“We're crossing our fingers that researchers will find a remedy for this awful illness.”

This report by The Canadian Press was first published Dec. 19, 2023.