Autoimmune Stiff Person Syndrome: Understanding Why Pain Happens

Stiff person syndrome (SPS) is a rare disorder that causes disabling muscle stiffness and spasms. It is an autoimmune neurological disorder that occurs when the body’s immune system attacks certain enzymes involved in muscle relaxation.

This condition affects approximately 1 out of 1 million people worldwide, with symptoms beginning between ages 20 and 50. Treatment can help slow progression and control symptoms, but there is no cure for stiff person syndrome. People can develop breathing difficulties as the condition progresses.

This article describes the symptoms, diagnostic process, and treatments of stiff person syndrome. 

Symptoms: How Does Stiff Person Syndrome Feel?

Stiff person syndrome causes painful stiffness, difficulty walking, problems maintaining balance, and trouble with moving the way you want to. As the condition worsens, it can cause falls, difficulty swallowing, vomiting, or constipation. It may make it hard to breathe.

If you have stiff person syndrome, you can have trouble with day-to-day activities, including self-care. And you might notice that you get startled easily, and the pain can become constant. The symptoms of stiff person syndrome are expected to worsen over time gradually.

The effects of stiff person syndrome occur due to muscle stiffness and muscle spasms, described as follows:

• Muscle stiffness: The muscle stiffness of stiff person syndrome can feel like the muscles are tight, sore, and difficult to move—but they are not paralyzed. Muscle stiffness can come and go, or it may be present all the time. It can affect your trunk and one or more of your extremities. As the disease progresses, you can expect muscle stiffness to occur more frequently, and it can eventually become constant.
• Muscle spasms: These episodes can last for seconds or longer. They look and feel like jerking movements of the muscles. Sometimes, muscle spasms can be painful or uncomfortable.

Triggers

People who have stiff person syndrome can be highly sensitive to sounds or touch. If you have been diagnosed with stiff person syndrome, you may experience worsening symptoms in response to triggers.

Triggers can include cold temperatures, sounds, touch, stress, or being startled. These triggers are so common that it is impossible to avoid them. You can also have worsening symptoms without any triggers.

Neurological and Autoimmune Effects in SPS

Stiff person syndrome is considered an autoimmune disease, which is a disease that develops when the body attacks its own tissue.

The symptoms occur due to a deficit of gamma-aminobutyric acid (GABA) in the nerves that control your muscles. GABA is a neurotransmitter that helps balance nerve activity throughout the body, preventing excess nerve activity. In stiff person syndrome, this deficiency prevents muscles from relaxing as they should.

Stiff person syndrome develops when the immune system attacks glutamic acid decarboxylase (GAD), an enzyme that is involved in production of GABA.

Risk Factors

There is no known underlying hereditary pattern or risk factor for developing stiff person syndrome. The condition is extremely rare, and there isn’t a gene or environmental exposure known to cause it.

Some people who have stiff person syndrome also have other immune system disorders, but having an immune system disorder does not mean that you are at risk for stiff person syndrome.

Sometimes stiff person syndrome develops as a paraneoplastic disorder. A paraneoplastic disorder is a condition in which cancer causes immune proteins to attack a very specific part of the body. Paraneoplastic syndromes are rare, and having stiff person syndrome does not necessarily mean that you have underlying cancer.

Treatments to Manage SPS Pain

Some treatments are available for managing stiff person syndrome. The treatments include medications or other interventions that can help with symptom management and immune treatments to control the underlying condition.

Treatments to relieve symptoms include:

• Pain medication: Examples include Keppra (levetiracetam) and Lyrica (pregabalin), which are used to treat nerve-related pain.
• Muscle relaxants: Examples include Lioresal (baclofen), Diastat (diazepam), and Zanaflex (tizanidine), which can be used to help the muscles relax and prevent spasms.
• Injected muscle relaxants: Injections can include Botox (onaotulinumtoxinA), which can temporarily paralyze the muscles to prevent spasms.
• Immune-modifying therapies: Corticosteroids, plasmapheresis (removing some immune proteins from the blood), intravenous immunoglobulin (IVIG), Prograf (tacrolimus), and Rituxin (rituximab) can help lower the body’s immune activity.

Immune-modifying medications have many side effects, including increasing the risk of infections, and there are no well-established protocols for their use in the treatment of stiff person syndrome.

There is no cure for stiff person syndrome, but research is ongoing to find better treatments and a potential cure.

SPS Diagnostic Process 

Generally, the diagnosis of stiff person syndrome can take weeks, months, or longer. It is such a rare disorder that more common neurological disorders are usually considered first before stiff person syndrome is diagnosed. 

The diagnosis of stiff person syndrome begins with a review of your symptoms, health history, family history, and a physical examination.

Your evaluation will then involve a consideration of common conditions that can cause symptoms similar to those of stiff person syndrome—multiple sclerosis (MS), Parkinson’s disease, radiculopathy (pinched nerve), neuropathy, Guillain-Barré syndrome, lupus, and others.

Depending on the stage of your condition and the signs and symptoms affecting you at the time of your evaluation, further testing would likely be needed.

Tests that you may need include:

• Brain imaging studies, which can help in diagnosing multiple sclerosis
• Spine imaging studies, which may help in diagnosing radiculopathy
• Electromyography or nerve conduction studies, which can help in diagnosing Guillain-Barré syndrome or peripheral neuropathy
• Blood tests, which can help in diagnosing inflammatory disorders, such as lupus
• Nerve or muscle biopsy, which can help in diagnosing some types of neuropathy or inflammatory disorders

There is no definitive test that defines stiff person syndrome, but most people with the condition have anti-GAD antibodies. If your neurologist is considering the possibility that you might have stiff person syndrome, they will order this blood test for you.

Specialists Involved in SPS Care

If you are diagnosed with stiff person syndrome, you will need medical care from a variety of healthcare providers. You may see some of these providers more frequently during the initial diagnostic process and others during the ongoing treatment phase of your care.

Providers that you may see include:

• Primary care provider (PCP): Your initial visit will likely be with a primary care provider, and you will likely also need to follow up periodically to get care for other medical conditions that come up (such as a cold) and for your healthcare screenings and maintenance.
• Neurologist: A neurologist is likely to evaluate your symptoms and order the diagnostic tests necessary to determine whether you have stiff person syndrome or another neurological disorder. Your neurologist will likely initiate a treatment plan and see you for follow-up visits and when you have changes in your symptoms.
• Physical therapist: A physical therapist can work with you to help you strengthen your muscles through exercises. While this doesn’t stop disease progression, physical therapy can help you maximize your muscle strength and can also help reduce or delay muscle atrophy (muscle thinning and weakness) as your disease progresses.
• Occupational therapist: An occupational therapist can work with you on exercises, modifications, and assistive devices that can help you with your ability to manage your day-to-day tasks, such as self-care, getting dressed, and doing practical things that you may need to do at home or work.
• Dietitian: Sometimes, stiff person syndrome may affect your ability to eat, and you may need to see a healthcare specialist who can help you select nutritious food that’s easy for you to swallow and digest.
• Pain-management specialist: Your PCP or neurologist may give you prescriptions or other treatments for managing pain. However, if the pain is persistent and severe, and it’s not responding well to standard treatments, you may need to see a pain management specialist. This is usually a physician specializing in anesthesiology, neurology, or physical medicine and rehabilitation who has additional training in pain management.
  

Well-Being Tips With SPS 

If you've been diagnosed with stiff person syndrome, it can be beneficial to join a support group or enroll in a clinical trial so you have access to the most updated information and treatments for this uncommon disease.

Coping involves practical strategies to help manage your symptoms and maintain your comfort while maximizing your quality of life. You and your loved ones may also need to seek professional support for help in dealing with the emotional aspects of living with this disease.

Tips for living with stiff person syndrome include:

• Use heating pads and maintain warmth through clothes, blankets, and temperature control, and decide whether these strategies help your muscles feel a little better.
• Find exercises that make you feel comfortable, energetic, and refreshed—this might include stretching, aerobics, or water exercises.
• Consider whether professional massage, acupuncture, or acupressure helps relieve discomfort or pain.
• Maintain self-care that helps you feel good about yourself, which may include spending time with friends and family, hobbies, or travel.
• Ask for a referral to a personal therapist or a family therapist so you can have the guidance and sounding board of a professional who is experienced in understanding the emotional aspects of the disease.

Summary 

Stiff person syndrome is a rare autoimmune neurological disorder. It causes muscle stiffness and spasms, which can interfere with your ability to move and manage daily self-care and other tasks. It can also cause discomfort or pain.

Because the condition is so rare, it can take time to get a diagnosis of stiff person syndrome—other, more common neurological conditions are usually considered first. If you are diagnosed with stiff person syndrome, you can expect lifelong care, usually involving a team of healthcare professionals.

Your treatment will include immune therapies to help manage and potentially slow down the disease, as well as symptomatic therapy to reduce the pain and spasms of stiff person syndrome. You may benefit from joining a support group or enrolling in a clinical trial to help you get access to the most updated treatments for this condition.