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Health and Disease

Stiff Person Syndrome (SPS)

Stiff Person Syndrome (SPS) is a debilitating neurological disease that causes a broad range of symptoms among patients. This article explores the symptoms, causes and treatment of the condition.

By Anujah Ramanan

Published 11:36 EST, Mon October 18th, 2021

SPS is an extremely rare neurological disease affecting roughly one in a million people. Many cases of the disease occur in conjunction with other autoimmune disorders such as diabetes and the progressive disease is known to impact twice as many women than men. The disease affects the muscles, causing stiffness and muscle spasms. Given that muscles are required to do so many activities, this disease can be extremely debilitating for sufferers. 

Symptoms

Disease progression exhibits much variability among different patients. For some, it may only take a few months for symptoms to heighten; for others, it may take several months thus allowing them to continue with their daily activities. As implied by the name of the disease, the disease is distinguished by muscle stiffness, pain and aches. During early stages of the disease, stiffness and expansion may be observed in the abdominal and trunk muscles. Further, symptoms may not be experienced constantly during this period. However, symptoms may become more persistent over time, presenting more frequently until eventually symptoms are experienced all the time. As the disease progresses, many more muscles in the body may be affected including muscles in the face. Muscle spasms are another symptom that characterise the disease and can last for any amount of time ranging between a few seconds to a couple of hours. These spasms can have various implications for a patient’s health depending on the duration and location in the body at which they occur. For example, patients may experience weight loss due to spasms of the abdominal muscles that cause them to feel full without having consumed much food. Other medical complications that can result from spasms include the dislocation of bones and respiratory issues where spasms occur in the chest. Muscle spasms are not always caused by a trigger but there are several factors that can cause the onset of spasms. Some of these triggers include cold temperatures and unforeseen loud noises.

Causes

The exact cause of the disease remains somewhat a mystery however research has attributed it to an autoimmune reaction located in the brain and spinal cord. Patients with the disease tend to have antibodies against glutamic acid decarboxylase (GAD). This protein is an enzyme which catalyses the conversion of glutamate to gamma-aminobutyric acid (GABA).  GABA is an inhibitory neurotransmitter and thereby reduces the chance that a neuron will fire an action potential. Thus it plays an important role in controlling neuronal excitability. In producing antibodies against GAD, the function of GABA is minimised thus leading to the symptoms experienced due to neurons firing when not required. It is common for patients with SPS to also be suffering from another autoimmune disease or certain types of cancer although this correlation remains unexplained. It is necessary to acknowledge that observable levels of antibodies against GAD are not strictly exhibited in all cases of SPS. When antibodies against GAD are not detected during diagnostic tests, one might test a patient for antibodies against the protein amphiphysin because these antibodies are observed in some SPS cases. However for some patients the disease remains idiopathic despite diagnostic tests.

Diagnosis  

A common test used in diagnosis is a blood test to determine whether the patient’s blood contains antibodies against GAD. Detectable levels of the antibody will be found in roughly 60 to 80% of patients suffering from the disease. Levels of the antibody against GAD may also be identified through performing a Lumbar puncture, otherwise known as a spinal tap.  This is a method that allows the collection of cerebrospinal fluid from which the antibody levels can be measured. Other elements of diagnosis include recording a detailed medical history and possibly conducting tests to eliminate the diagnosis of other diseases that present similar symptoms to SPS. Electromyography is another test that may be carried out; this facilitates the observation of electrical activity in skeletal muscles. In patient suffering from SPS, ceaseless motor activity would be recorded and readings above a certain value may indicate that a patient has SPS.

Treatment

Treatment of the disease focuses on treating symptoms in order to improve the quality of life of patients. As individuals experience varying symptoms, treatment plans are often quite specific to the individual. For example diazepam is often prescribed, targeting the issue of muscle stiffness. Meanwhile other drugs administered may target the immune system given that symptoms are believed to be a result of elevated levels of the antibody against GAD. Some clinical research has highlighted the effectiveness of administering intravenous immunoglobulin to relieve symptoms. A study conducted in 2005 showed that stiffness had significantly decreased across a couple of months of receiving intravenous immunoglobulin and it enabled them to complete activities that they were previously limited from. However the study only observed patients who had observable levels of antibodies against GAD in their blood therefore it is undetermined whether this treatment would be effective in patients who do not have these antibodies. Further, this treatment can also be associated with serious side effects among certain circumstances, emphasising the importance of further research and personalised treatment for the disease. Other aspects of treatment may include physiotherapy and aqua therapy in order to aid and preserve mobility. There are several other treatments that are being investigated for safety and efficacy such as plasmapheresis (also known as plasma exchange). This procedure seeks to target the role played by the immune system in the disease by removing the unwanted substances from the blood which in this case, would be the antibodies against GAD.

 Who is at risk of developing the disease?

In several instances, cases of the disease occur with no related medical history in the family. However there have also been cases in which members of the same family have the disease thus indicating the possibility of genetically inheriting the disease. At present, a specific gene mutation has not been identified to cause the disease. Additionally, research suggests that patients most commonly present with the disease between the ages of 30 and 60 though people outside of this age range may also suffer from the condition.

 Conclusion

Although the pathophysiology of the disease is not completely clear, many treatments show promise for improving patient quality of life. Variability in the presentation of symptoms across different patients emphasises the importance of personalised medicine for this condition. Research has highlighted the significance of assessing the potential consequences of certain novel treatments for individual patients.

Anujah Ramanan, Youth Medical Journal 2021

References

1)      NORD (National Organization for Rare Disorders). (n.d.). Stiff Person Syndrome. [online] Available at: https://rarediseases.org/rare-diseases/stiff-person-syndrome/.

2)      Yale Medicine. (n.d.). Stiff Person Syndrome. [online] Available at: https://www.yalemedicine.org/conditions/stiff-person-syndrome

 3)      rarediseases.info.nih.gov. (n.d.). Stiff person syndrome | Genetic and Rare Diseases Information Center (GARD) – an NCATS Program. [online] Available at: https://rarediseases.info.nih.gov/diseases/5023/stiff-person-syndrome.

4)      Cleveland Clinic. (n.d.). Stiff Person Syndrome: Symptoms, Causes, Treatment, Outlook. [online] Available at: https://my.clevelandclinic.org/health/articles/6076-stiff-person-syndrome

5)     Dalakas, M.C. (2005). The role of IVIg in the treatment of patients with stiff person syndrome and other neurological diseases associated with anti-GAD antibodies. Journal of Neurology, [online] 252 Suppl 1, pp.I19-25. Available at: https://pubmed.ncbi.nlm.nih.gov/15959668/

By Anujah Ramanan

Anujah Ramanan is a student at North London Collegiate School in London, England. She is interested in the fields of Epigenetics, public health and Immunology.

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