(WGN-TV) You probably hadn’t heard of stiff-person syndrome until superstar singer Celine Dion announced her battle with the rare and often misdiagnosed ailment in December.

The disease “is characterized by fluctuating muscle rigidity in the trunk and limbs and a heightened sensitivity to stimuli such as noise, touch, and emotional distress, which can set off muscle spasms,” according to the National Institute of Neurological Disorders and Stroke (NINDS).

In a message to her fans, Dion gave voice to the 1-in-1-million people struggling with the same disorder she had been battling offstage.

“I’ve been dealing with problems with my health for a long time, and it’s been really difficult for me to face these challenges and to talk about everything that I’ve been going through,” the Canadian singer said before revealing her diagnosis. “We now know this is what’s been causing all of the spasms that I’ve been having.”

“My mind was, ‘Oh my goodness, I feel so bad for her,’” said Moira Papp. The 54-year-old was diagnosed with stiff-person syndrome in 2021. “But I was very happy because I knew she has a humongous voice and this is going to get recognized.” 

“I did notice I was falling, but I attributed it to tripping or going too fast. I was falling up and down the stairs,” Papp said, as she described symptoms of the syndrome.

Before Papp got the right diagnosis, she said doctors thought it might be multiple sclerosis, then cervical spine stenosis.

“There’s no single absolute characteristic that separates it from other diseases, so people look for things like: Did they have a stroke? Have they had damage to their spinal cord? Do they have Parkinson’s disease?” said Dr. David Randall, a neurologist at Advocate Health Care. “So there’s other neurologic diseases that may share some of the difficulties with walking and the feeling of stiffness.”

“Everyone’s like, ‘What do you have?’” Papp said. “And then it takes forever to talk about it because you have to talk about how rare it is.”

Most patients go years without a proper diagnosis.

“I’ve had MRIs, CTs, PET scans, I mean all of it numerous times,” Papp said.

Signs of SPS don’t necessarily show up on imaging, but there are biomarkers that help doctors make the call. Papp has an elevated protein called GAD-65 in her blood.

“It’s an autoimmune disease as best we know and it recognizes a protein that we need as being foreign,” Randall said. “And it attacks that protein and that stops the control of the muscle tightness.”

Papp’s treatment regimen includes weekly infusions of immunoglobulin, a drug that targets her overactive immune system.

People with stiff-person syndrome often have a hunched-over or stiff posture, and may have trouble walking or moving. Some people may be “afraid to leave the house because street noises, such as the sound of a horn, can trigger spasms and falls,” NINDS explains, and without normal reflexes they may be injured more easily.

“Somebody can be just walking along and they get terrible muscle stiffness and they drop to the ground,” Randall said. “And so there are injuries associated with that as well.”

“I’ve learned that a stiff person has to move,” Papp said. “You cannot sit around and lay around in bed. Even if you don’t feel like moving you have to move. So I have a whole new friend group at the health club because I’m there every day.”

Even muscles involved in breathing, swallowing and speech can be affected. According to Dion, muscle spasms have impacted her vocal cords.

While Papp never sang before her diagnosis, she has since taken it up. She recently performed on stage for the first time.

“Maybe there’s something in me that says, ‘You know what? You gotta live life to the fullest!’” she said.

Stiff-person syndrome typically progresses over 10 to 20 years, but doctors say they have treatments to offer patients cope with the degenerative disease.