Céline Dion's muscle spasms caused by rare disorder: What is stiff-person syndrome?

Singer Céline Dion was recently diagnosed with a rare neurological disorder called stiff-person syndrome, which has caused her to experience severe muscle spasms, the iconic performer announced Dec. 8 in an Instagram video.

"We now know this is what's been causing all of the spasms that I've been having," Dion said in the video. "Unfortunately, these spasms affect every aspect of my daily life, sometimes causing difficulties when I walk and not allowing me to use my vocal chords to sing the way I'm used to."

Due to these symptoms, the singer previously postponed the opening of a new Las Vegas show, originally set to open in 2021, and postponed and canceled shows in her "Courage World Tour," which had been pushed to 2022 after being interrupted by the COVID-19 pandemic's start in 2020. Dion has now announced that she'll be postponing her scheduled spring performances and canceling her summer shows. 

"For me to reach you again, I have no choice but to concentrate on my health at this moment, and I have hope that I'm on the road to recovery," Dion said. 

Stiff-person syndrome affects an estimated 1 to 2 in 1 million people, according to Johns Hopkins Medicine. It affects twice as many women as it does men, the Genetic and Rare Diseases Information Center (GARD) states.

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The syndrome is likely caused by the immune system inadvertently attacking nerve cells in the brain and spinal cord. These nerve cells would normally help control muscle contractions, so as the nerve cells are progressively destroyed, patients experience spontaneous stiffness in the torso and limbs, as well as sporadic and violent muscle spasms. Loud noises, sudden movements and emotional distress can trigger these spasms, which can sometimes be forceful enough to fracture bone, according to GARD.

One autoimmune reaction thought to cause the syndrome specifically targets an enzyme called glutamic acid decarboxylase (GAD), which is needed to produce the chemical messenger GABA, according to Yale Medicine. GABA serves as a brake for muscle-controlling nerve cells, so when there's too little GABA, that brake gets released and the cells can shift into overdrive. 

An estimated 60% to 80% of patients with the syndrome carry antibodies against GAD, while others with the disorder may carry other antibodies or show other signs of autoimmunity. Certain GAD antibodies are also found in people with type 1 diabetes, in which the immune system attacks insulin-producing cells in the pancreas. People with stiff-person syndrome often have type 1 diabetes or another autoimmune disorder, such as vitiligo or pernicious anemia. People with certain types of cancer also have an elevated risk of developing the syndrome, although it's not clear why, according to Yale.

There's no cure for stiff-person syndrome, so treatments are aimed at relieving symptoms. In general, drugs used to treat the syndrome act as a stand-in for the patient's missing GABA or help suppress their harmful autoimmune activity, Dr. Scott Newsome, director of Johns Hopkins' Stiff Person Syndrome Center, said in an informational video. These treatments can include sedatives, muscle relaxants, steroids and immunotherapies. 

Botulinum toxin (BOTOX) may also be used to treat muscle spasms and rigidity, and various physical and occupational therapies can also be helpful to patients. 

The severity of symptoms and rate of decline varies between people; some see their symptoms stabilize for a time while others steadily worsen, according to the Cleveland Clinic. Although the syndrome can be managed with treatment, it can lead to complications that shorten life expectancy.