Stiff person syndrome (SPS) is an autoimmune neurological disorder. Like other types of neurological disorders, SPS affects your brain and spinal cord (central nervous system).

An autoimmune disorder occurs when your immune system incorrectly identifies normal body tissues as harmful and attacks them.

SPS is rare. It can significantly affect your quality of life without proper treatment.

Most notably, SPS causes muscle stiffness. Early symptoms include:

  • limb stiffness
  • stiff muscles in the trunk
  • posture problems from a rigid back muscles (this can cause you to hunch over)
  • painful muscle spasms
  • walking difficulties
  • sensory issues, such as sensitivity to light, noise, and sound
  • excessive sweating (hyperhidrosis)

Spasms due to SPS can be very strong and may cause you to fall if standing. Spasms can sometimes be strong enough to break bones. Spasms are worse when you’re anxious or upset. Spasms can also be triggered by sudden movements, loud noise, or being touched.

When you’re living with SPS, you may also have depression or anxiety. This may be caused by other symptoms you might be experiencing or a decrease in neurotransmitters in the brain.

The potential for emotional distress can increase as SPS progresses. You may notice spams worsen when you’re out in public. This may lead to developing anxiety about going out in public.

In the later stages of SPS, you may experience increased muscle stiffness and rigidity.

Muscle stiffness can also spread to other parts of your body, such as your face. This can include muscles used for eating and talking. Muscles involved in breathing may also be affected causing life-threatening problems breathing.

Due to the presence of amphiphysin antibodies, SPS may place some people at an increased risk for certain cancers, including:

  • breast
  • colon
  • lung

Some people with SPS may develop other autoimmune disorders, including:

  • diabetes
  • thyroid problems
  • pernicious anemia
  • vitiligo

The exact cause of SPS is unknown. It’s possibly genetic.

You may also be at an increased risk for developing the syndrome if you or someone in your family has another type of autoimmune disease. These include:

For unknown reasons, autoimmune diseases attack healthy tissues in the body. With SPS, tissues in the brain and spinal cord are affected. This causes symptoms based on the tissue that’s attacked.

SPS creates antibodies that attack proteins in brain neurons that control muscle movements. These are called glutamic acid decarboxylase antibodies (GAD).

SPS typically occurs in adults between ages 30 and 60. It’s also twice as common in women compared to men.

To diagnose SPS, your doctor will look at your medical history and perform a physical exam.

Testing is also essential. First, a blood test may be administered to detect GAD antibodies. Everyone with SPS doesn’t have these antibodies. However, up to 80 percent of people living with SPS do.

Your doctor may order a screening test called an electromyography (EMG) to measure muscular electrical activity. Your doctor may also order an MRI or lumbar puncture.

SPS may be diagnosed along with epilepsy. Sometimes its mistaken for other neurological disorders, such as multiple sclerosis (MS) and Parkinson’s disease.

There’s no cure for SPS. However, treatments are available to help you manage your symptoms. Treatment may also stop the condition from getting worse. Muscle spasms and stiffness may be treated with one or more of the following medications:

  • Baclofen, a muscle relaxer.
  • Benzodiazepines, such as diazepam (Valium) or clonazepam (Klonopin). These medications relax your muscles and help with anxiety. High doses of these medications are often used to treat muscle spasms.
  • Gabapentin is a type of drug used for nerve pain and convulsions.
  • Muscle relaxers.
  • Pain medications.
  • Tiagabine is an anti-seizure medication.

Some people with SPS have also experienced symptom relief with:

  • Autologous stem cell transplant is the process where your blood and bone marrow cells are collected and multiplied before transferring back to your body. This is an experimental treatment that’s only considered after other treatments have failed.
  • Intravenous immunoglobin can decrease the number of antibodies that attack healthy tissues.
  • Plasmapheresis is a procedure in which your blood plasma is traded with new plasma to reduce the number of antibodies in the body.
  • Other immunotherapies such as rituximab.

Antidepressants, such as selective serotonin reuptake inhibitors (SSRIs) may help with depression and anxiety. Zoloft, Prozac, and Paxil are among the brands your doctor might suggest. Finding the right brand often takes a trial and error process.

In addition to medications, your doctor may refer you to a physical therapist. Physical therapy alone can’t treat SPS. However, the exercises may significantly help with your:

  • emotional well-being
  • walking
  • independence
  • pain
  • posture
  • overall day-to-day function
  • range of motion

Depending on how severe your symptoms are, your physical therapist will guide you through mobility and relaxation exercises. With the help of your therapist, you may even be able to practice some movements at home.

If you’re living with this condition, you’re more prone to falls because of a lack of stability and reflexes. This can increase your risk for severe injuries and even permanent disability.

In some cases, SPS can progress and spread to other areas of your body.

There’s no cure for SPS. However, treatments are available to help you manage your symptoms. Your overall outlook depends on how well your treatment plan works.

Everyone responds to treatment differently. Some people respond well to medications and physical therapy, while others may not respond as well to treatment.

Discuss your symptoms with your doctor. It’s especially important to discuss any new symptoms you’re experiencing or if you aren’t seeing any improvements. This information can help them decide on a treatment plan that works best for you.