Stiff-person syndrome often occurs in people with type 1 diabetes, certain autoimmune disorders, or certain kinds of cancer.
Muscles gradually become stiffer and enlarge, starting in the trunk and abdomen but eventually affecting muscles throughout the body.
Doctors suspect stiff-person syndrome based on symptoms but use electromyography and blood tests to help confirm the diagnosis.
Treatment focuses on relieving symptoms and can include diazepam (a sedative), baclofen (a muscle relaxant), corticosteroids, and sometimes rituximab or plasma exchange.
Stiff-person syndrome (formerly called stiff-man syndrome) affects mainly the brain and spinal cord (the central nervous system), but it causes symptoms similar to those of some peripheral nerve disorders.
Stiff-person syndrome is more common among women and often occurs in people with type 1 diabetes, certain autoimmune disorders (such as thyroiditis Hashimoto Thyroiditis Hashimoto thyroiditis is chronic, autoimmune inflammation of the thyroid gland. Hashimoto thyroiditis results when antibodies in the body attacks the cells of the thyroid gland—an autoimmune... read more ), or certain kinds of cancer, including breast cancer (most commonly), lung cancer, kidney cancer, thyroid cancer, colon cancer, and Hodgkin lymphoma Hodgkin Lymphoma Hodgkin lymphoma is a cancer of a type of white blood cell called lymphocytes and is distinguished from other lymphomas by the presence of a particular kind of cancer cell called a Reed-Sternberg... read more .
The cause of stiff-person syndrome may be an autoimmune reaction Autoimmune Disorders An autoimmune disorder is a malfunction of the body's immune system that causes the body to attack its own tissues. What triggers an autoimmune disorder is not known. Symptoms vary depending... read more —when the body produces antibodies that attack its own tissues. In stiff-person syndrome, these antibodies attack nerve cells in the spinal cord that control muscle movement. Most people with stiff-person syndrome have antibodies that attack an enzyme called glutamic acid decarboxylase. This enzyme is involved in the production of a chemical messenger (neurotransmitter) that helps prevent nerves from overstimulating muscles. When less of this enzyme is produced, nerves overstimulate muscles, which become tight and stiff.
Sometimes the cause of stiff-person syndrome is unknown.
Symptoms of Stiff-Person Syndrome
In people with stiff-person syndrome, muscles of the trunk and abdomen gradually become stiffer and enlarge. Muscles of the arms and legs are affected less.
Usually, stiff-person syndrome progresses, leading to disability and stiffness throughout the body.
Diagnosis of Stiff-Person Syndrome
Electromyography
Blood tests
The diagnosis of stiff-person syndrome is suggested by symptoms. Tests are done to help confirm the diagnosis. They include electromyography Electromyography Diagnostic procedures may be needed to confirm a diagnosis suggested by the medical history and neurologic examination. Imaging tests commonly used to diagnose nervous system (neurologic) disorders... read more 
and blood tests to detect the antibodies that are present in many people with stiff-person syndrome.
Treatment of Stiff-Person Syndrome
Diazepam (a sedative) or another drug to relax the muscles
Immune globulin
Sometimes corticosteroids
Sometimes rituximab or plasma exchange
Treatment of stiff-person syndrome focuses on relieving symptoms. The sedative diazepam can consistently relieve the muscle stiffness. If diazepam is ineffective, other drugs, such as baclofen (a muscle relaxant), may be tried.
Immune globulin (a solution containing many different antibodies collected from a group of donors), given by vein (intravenously), may help relieve symptoms for up to a year.
Corticosteroids Corticosteroids Rheumatoid arthritis is an inflammatory arthritis in which joints, usually including those of the hands and feet, are inflamed, resulting in swelling, pain, and often destruction of joints.... read more 
can help but, if taken for a long time, have many side effects.
If immune globulin does not help, rituximab (a drug that modifies the immune system's activity) or plasma exchange Plateletpheresis (platelet donation) In addition to normal blood donation and transfusion, special procedures are sometimes used. In plateletpheresis, a donor gives only platelets rather than whole blood. Whole blood is drawn from... read more , which involves filtering toxic substances (including the abnormal antibodies) from the blood, is sometimes tried.
