Late last year, singer Celine Dion announced that she had been diagnosed with stiff person syndrome—a rare autoimmune disease that causes muscle spasms and extreme tightness—and would postpone all tour dates until 2024.

"Unfortunately, these spasms affect every aspect of my life, sometimes causing difficulties when I walk and not allowing me to use my vocal cords to sing the way I'm used to," the 54-year-old Canadian said in a video she posted on Instagram.

What is Stiff Person Syndrome?

It is estimated that stiff person syndrome affects one out of every 1 to 2 million people, but the incidence is most likely much higher because it is often misdiagnosed, says Marinos C. Dalakas, MD, FAAN, professor of neuromuscular medicine at Thomas Jefferson University in Philadelphia. It was first described in 1956 by two doctors whose patients reported painful muscle spasms as well as tightness in their thighs, back muscles, and abdomens.

Originally called stiff man syndrome and later stiff person syndrome because it more frequently affects women, the condition is part of stiff person spectrum disorder, so-called because a small number of people may have other overlapping symptoms such as ataxia (poor muscle control that causes clumsy movements), certain movement disorders, encephalitis, or autoimmune epilepsy in addition to stiff person syndrome.

Symptoms of stiff person syndrome include muscle stiffness, abnormal walking, and episodic muscle spasms triggered by unexpected tactile, visual, acoustic, or stressful events. People with severe disease may experience trouble walking and be at risk for falls. More rarely, they may have episodes of severe spasms that lock up their bodies and cause breathing problems, and may require hospitalization, Dr. Dalakas says.

Diagnosis of Stiff Person Syndrome

The condition is associated with antibodies, most often against the enzyme glutamic acid decarboxylase (GAD), which is detected at very high levels in about 70 to 80 percent of people with the condition, indicating an underlying autoimmune process.

Doctors conduct a thorough patient history and examination as well as an MRI of the brain and spine to rule out other causes. They also perform blood tests for these antibodies, high levels of which confirm a diagnosis of stiff person spectrum disorder. If the levels are low, doctors perform a lumbar puncture to examine the presence of these antibodies in the spinal fluid. An electromyogram (EMG), which assesses the excitability of the muscles, is helpful in making a diagnosis, especially in people with low or undetectable levels of GAD antibody, says Dr. Dalakas.

During an EMG, an acupuncture-sized needle is inserted into the muscle, allowing doctors to detect spontaneous electrical activity when the muscle is at rest—activity that’s absent in normal muscles—while also looking for signs of muscle hyperexcitability.

Conditions such as type 1 diabetes and Hashimoto’s thyroiditis (an autoimmune disorder that affects the thyroid and results in a decline in hormone production) can be associated with stiff person spectrum disorder. A small percentage of individuals may have an underlying malignancy. Accordingly, doctors may order CT scans and other tests, if clinically indicated, to check for those other diseases.

Treatment of Stiff Person Syndrome

Medications can help alleviate the symptoms, says Natalie Witek, MD, assistant professor of neurologic sciences at Rush University in Chicago. For example, benzodiazepines such as diazepam (Valium), alprazolam (Xanax), and clonazepam (Klonopin); muscle relaxants like baclofen (Lioresal); antiseizure medications such as gabapentin (Neurontin) and valproate (Depakote) can ease muscle spasms and stiffness. Symptomatic therapies can cause sleepiness and other side-effects, and if not well tolerated or fully effective, doctors treat the underlying autoimmune process with medications such as intravenous Immunoglobulin, says Dr. Dalakas.

Some people with the condition may be able to come off therapies like benzodiazepines and live comfortable and productive lives, especially with the use of immunotherapies, but many relapse and their condition may progress, says Dr. Witek. “Usually there are periods of fewer spasms and attacks, and there may be flare-ups,” she adds. “The number of spasms—which can be triggered by touch, fear, anxiety, and being startled—also can fluctuate.”

Dr. Witek feels grateful that someone as influential as Celine Dion has called attention to this sometimes devastating yet often treatable condition. “Her vulnerability and speaking out have raised awareness for a disorder that is underdiagnosed.”

Resources for Stiff Person Syndrome Spectrum Disorder

• International Parkinson and Movement Disorder Society: movementdisorders.org; 414-276-2145
• National Institute of Neurological Disorders and Stroke: ninds.nih.gov; 800-352-9424
• National Organization for Rare Disorders: rarediseases.org; 617-249-7300
• Stiff Person Syndrome Research Foundation: stiffperson.org; info@stiffperson.org