What is stiff person syndrome? Celine Dion's incurable disorder explained

As Celine Dion opens up about the health problems forcing her to postpone and cancel some of her performances, she’s putting the spotlight on stiff person syndrome.

In a video posted on Dion’s Instagram page on Thursday, Dec. 8, the singer explains she was recently diagnosed with the disorder.

“We now know this is what’s been causing all of the spasms that I’ve been having,” Dion, 54, said.

“Unfortunately, these spasms affect every aspect of my daily life, sometimes causing difficulties when I walk and not allowing me to use my vocal cords to sing the way I’m used to. … I’m working hard with my sports medicine therapist every day to build back my strength and my ability to perform again, but I have to admit it’s been a struggle.”

What is stiff person syndrome?

Researchers call it a neurological disorder with features of an autoimmune disease. It causes muscle stiffness in a person’s torso and limbs, and a heightened sensitivity to noise, touch and emotional stress, which can set off painful muscle spasms, according to the National Institute of Neurological Disorders and Stroke.

Stiff person syndrome is very rare, with only one or two people in a million affected, Johns Hopkins Medicine in Baltimore, Maryland, noted. It affects twice as many women as men, according to the National Institutes of Health.

It’s a "very serious condition," says Dr. Desimir Mijatovic, a pain medicine specialist with the Cleveland Clinic in Ohio.

“People can have difficulty with movement and difficulty with living their lives,” Mijatovic tells TODAY.com.

Speaking about Dion specifically, he notes there are many muscles involved with singing, especially when a singer performs in front of a huge audience. “Those muscles are prone to spasm, or tightening up, and I’m sure it can affect the way that she sings and performs,” Mijatovic says. “If those muscles aren’t working properly, that can make it very difficult.”

Dr. Scott Newsome, director of the Stiff Person Syndrome Center at Johns Hopkins Medicine, called it “a devastating disease” in a video explaining the disorder.

“It’s quite painful so people will go around with these chronic pain syndromes, go from one doctor to another trying to figure out what’s causing these really bad spasm pain syndromes. Sometimes they get labeled crazy.”

Because stiff person syndrome is so rare and can mimic other conditions, it takes about seven years on average for people to get diagnosed, Newsome added.

What are the symptoms?

Patients may initially feel an aching discomfort, stiffness or pain, especially in the lower back or legs, but also in the shoulders, neck, and hips, according to the National Organization for Rare Disorders.

With time, the leg muscles stiffen, with one leg often more affected than the other, leading to a stiff walking gait and a hunched over posture, it noted.

"I often can’t move because the pain and muscle stiffness is overwhelming," Jane Lees, who has stiff person syndrome and lives in Indianapolis, previously told TODAY.

Patients also develop muscle spasms, which can be triggered by common sounds such as a car horn honking, "causing people to freeze like a statue and fall," according to the Stiff Person Syndrome Research Foundation.

“Just walking down the street, they could have a spasm and fall,” Newsome said.

Not being able to get regular sleep, loud noises and stressful situations can worsen the symptoms, Mijatovic notes.

What causes stiff person syndrome?

The exact cause is still a mystery, but it appears to be an autoimmune response gone awry in the brain and spinal cord, according to the NIH.

The disorder is frequently associated with other autoimmune diseases, such as diabetes, thyroiditis, vitiligo and pernicious anemia, it added.

How is the disorder diagnosed and treated?

Since the symptoms mimic other conditions, it can be difficult to diagnose. People with the syndrome have elevated levels of certain antibodies in their blood, so a definitive diagnosis can be made with a blood test that measures those levels, the NIH noted.

There’s no cure, but intravenous immunoglobulin treatment, medications to control muscle spasms, anticonvulsants and other drugs can help, according to the NIH. Physical, occupational and aqua therapy is also an important part of the treatment, according to Yale Medicine.

Patients potentially have to take medications on a regular basis to manage the life-disrupting symptoms, Mijatovic says.

“A lot of people are able to make recovery to the point that their condition is stable. They’re not worsening anymore. They can continue to live fairly mobile (lives),” he notes, adding that it’s possible Dion can recover to the point where she is performing again.

“People like Celine are oftentimes able to overcome a lot of amazing things, and I definitely think it’s something that’s possible, and it’s something that I’m sure a lot of people look forward to.”

TODAY's Maura Hohman contributed to this report.

This article was originally published on TODAY.com