Neurological Disorders What Is Stiff-Person Syndrome (SPS)? By Sanjana Gupta Sanjana Gupta Sanjana is a health writer and editor. Her work spans various health-related topics, including mental health, fitness, nutrition, and wellness. Learn about our editorial process Updated on January 03, 2023 Medically reviewed Verywell Mind articles are reviewed by board-certified physicians and mental healthcare professionals. Medical Reviewers confirm the content is thorough and accurate, reflecting the latest evidence-based research. Content is reviewed before publication and upon substantial updates. Learn more. by Shaheen Lakhan, MD, PhD, FAAN Medically reviewed by Shaheen Lakhan, MD, PhD, FAAN Shaheen Lakhan, MD, PhD, is an award-winning physician-scientist and clinical development specialist. Learn about our Medical Review Board Print DjelicS/E+/Getty Table of Contents View All Table of Contents Symptoms Types Causes Diagnosis Treatment Stiff-person syndrome is a neurological disorder that is characterized by muscle stiffness and painful muscle spasms. It is a rare condition that only affects one or two persons in every million people. It is estimated that fewer than 5,000 people in the United States live with this condition. This article explores the types, causes, symptoms, and diagnosis of stiff-person syndrome, as well as some treatment options and coping strategies that may be helpful. Symptoms of Stiff-Person Syndrome The main symptoms of stiff-person syndrome are muscle stiffness and muscle spasms. Muscle Stiffness The muscles in the torso (chest, back, and abdomen) and sometimes the limbs (arms and legs) become stiff and rigid, which can be painful and uncomfortable. The stiffness may spread to other areas of the body and either fluctuate in intensity or get progressively worse. Over time, the person may develop a hunched posture, which can make it hard for them to walk and perform other everyday activities. Muscle Spasms Muscle stiffness is often alternated with episodes of painful muscle spasms. The muscle spasms typically last a few seconds or minutes, but can sometimes last for a few hours. They may affect specific parts of the body or the entire body. The spasms may be so severe in intensity that they can cause the person to fall down. The muscle spasms may be triggered by: LightLoud or unexpected noisesSudden movementsTemperature changesEmotional stressPhysical touch or stimulation Emotional Symptoms In addition to physical symptoms, people with stiff-person syndrome may also experience emotional symptoms such as depression, anxiety, and phobias. For instance, someone with stiff-person syndrome may develop agoraphobia, which is a fear of leaving home or going to open or crowded places. Leaving the house can be scary because a loud sound such as the sound of a car horn can trigger a disabling muscle spasm that may cause them to fall down. Types of Stiff-Person Syndrome The different types of stiff-person syndrome include: Classic stiff-person syndromeFocal stiff-person syndromeJerking stiff-person syndromeProgressive encephalomyelitis with rigidity and myoclonus (PERM)Paraneoplastic-related stiff-person syndrome The Mental Health Effects of Chronic Pain Causes of Stiff-Person Syndrome While the exact causes of stiff-person syndrome are unknown, research indicates that it is caused by a faulty autoimmune response in the brain and spinal cord. It is therefore classified as an autoimmune disorder. Autoimmune disorders are a group of conditions wherein the person’s immune system mistakenly attacks and harms their healthy cells. While there are different types of autoimmune disorders, stiff-person syndrome is a type of autoimmune disorder that causes the muscles to fail to work the way they should. This is challenging because we rely on the strength and support of our muscles for every action we do, including walking, sitting, standing, and typing. In people with stiff-person syndrome, their immune system attacks a protein in the body known as glutamic acid decarboxylase (GAD), by creating GAD antibodies. GAD is an enzyme that is required to make a neurotransmitter known as gamma-aminobutyric acid (GABA), which helps control muscle movement by decreasing the activity of motor neurons. Low levels of the GABA neurotransmitter can cause motor neurons to fire excessively, even when they’re not supposed to. However, the association between GAD antibodies and stiff-person syndrome is still being researched, because some people with GAD antibodies don’t have stiff-person syndrome and some people with stiff-person syndrome don’t have any unusual antibodies. Approximately 60% to 80% of people with stiff-person syndrome have GAD antibodies in their blood and spinal fluid. These are some of the risk factors that can make a person more likely to develop stiff-person syndrome: Gender: Stiff-person syndrome affects twice as many women and people assigned female at birth than men and people assigned male at birth. Age: The symptoms of stiff-person syndrome tend to appear between the ages of 30 and 40. Autoimmune conditions: Stiff-person syndrome is often associated with the presence of other auto-immune conditions such as celiac disease, vitiligo, pernicious anemia, autoimmune thyroid disease, and type 1 diabetes. Cancer: Stiff-person syndrome is more prevalent in people who have certain forms of cancer, such as lung cancer, breast cancer, colon cancer, thyroid cancer, kidney cancer, and lymphomas. How Does Stress Impact the Immune System? Diagnosing Stiff-Person Syndrome Stiff-person syndrome can be difficult to diagnose because it is a rare condition and its symptoms are often mistaken for those of other conditions such as multiple sclerosis, fibromyalgia, or Parkinson’s disease. The diagnostic process may therefore involve several tests to confirm the symptoms and rule out other health conditions. The diagnostic process may include the following tests: Antibody blood test: A blood test can check for the presence of GAD antibodies as well as unusual levels of other antibodies in the blood.Electromyography (EMG): An electromyography test detects the electrical activity levels in the muscles, in order to rule out other health conditions.Lumbar puncture: Also known as a spinal tap, a lumbar puncture test involves using a needle to draw fluid from the spinal canal. The fluid is then tested for GAD antibodies. 5 Questions to Ask Yourself After an Initial Diagnosis Treating Stiff-Person Syndrome Treatment for stiff-person syndrome may involve medical and non-medical interventions. Non-Medical Interventions There are several therapies that help relax the muscles and relieve pain, such as: Stretching Aqua therapy Heat therapy Massage Acupuncture Speech therapy Occupational therapy Physical therapy Medications The symptoms of stiff-person syndrome can be managed with medications such as: GABA-ergic agonist drugs, known as benzodiazepines, such as diazepam and clonazepam, which can help treat muscle stiffness and muscle spasms. Muscle relaxants, such as baclofen, which may also be prescribed along with benzodiazepines. Anti-seizure drugs, including pregabalin, vigabatrin, valproate, and gabapentin. Immunomodulating Therapies Research shows that certain immunomodulating therapies such as plasmapheresis and intravenous immunoglobulin (IVIG) can also help improve the symptoms of stiff-person syndrome. A Word From Verywell If you or a loved one have been diagnosed with stiff-person syndrome, you may find it difficult to cope with the symptoms and reality of living with the condition. It can be helpful to visit a mental healthcare provider to process your feelings and develop coping strategies. You may also benefit from joining a support group of people living with stiff-person disorder or other autoimmune conditions, as they can be a source of advice, resources, and a shared sense of understanding. 7 Sources Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. National Organization for Rare Disorders. Stiff-person syndrome. Ortiz JF, Ghani MR, Morillo Cox Á, et al. Stiff-person syndrome: A treatment update and new directions. Cureus. 2020;12(12):e11995. doi:10.7759/cureus.11995 National Institutes of Health. Stiff-person syndrome. Buechner S, Florio I, Capone L. Stiff-person syndrome: A rare neurological disorder, heterogeneous in clinical presentation and not easy to treat. Case Rep Neurol Med. 2015;2015:278065. doi:10.1155/2015/278065 National Institute of Neurological Disorders and Stroke. Stiff-person syndrome. Johns Hopkins Medicine. What are common symptoms of autoimmune disease? Yale Medicine. Stiff-person syndrome. By Sanjana Gupta Sanjana is a health writer and editor. Her work spans various health-related topics, including mental health, fitness, nutrition, and wellness. See Our Editorial Process Meet Our Review Board Share Feedback Was this page helpful? Thanks for your feedback! What is your feedback? Other Helpful Report an Error Submit Speak to a Therapist Online Advertiser Disclosure × The offers that appear in this table are from partnerships from which Verywell Mind receives compensation.