Stiff person syndrome (original term, Stiff man syndrome)

“Classic” stiff person syndrome (SPS) features stiffness, anti-glutamic acid decarboxylase (anti-GAD) antibodies, and other findings (1,2)

• dates back to as long as 1956 where Moersch and Woltman first described the tightness of the back, abdominal, and thigh muscles in 14 patients
  
  
• is a rare neurological disorder, which is an autoimmune disorder frequently associated with the presence of serum anti-glutamic acid decarboxylase (GAD) antibody
  
  
• characterised by fluctuating muscle rigidity and spasms
  • are many variants of SPS, these include the classical SPS, Stiff Leg Syndrome (SLS), paraneoplastic variant, gait ataxia, dysarthria, and abnormal eye movements
    
    
• SPS has an estimated prevalence rate of 1 per million per year and classic SPS affects women twice as many as men, almost all in the 20-60 year range (median age is 40 years) (2)
  
  
• incidence rate remains very low because the diagnosis of SPS is difficult in clinical practice, with only about 60%-80% of classic SPS cases seropositive for anti-GAD Ab (2)
  
  
• exact pathophysiology of SPS is unclear

SPS is strongly associated with other autoimmune diseases, such as (2):

• type 1 diabetes mellitus (T1DM),
• autoimmune thyroid disease (AITD),
• pernicious anemia,
• vitiligo,
• and Sjogren syndrome

Most patients have autoantibodies to glutamic acid decarboxylase.

Electromyographic (EMG) findings are supportive of continuous motor activity

Management

• seek expert advice
• aim is to improve symptoms
  • agents used in this condition include GABAergic agonists, such as diazepam or other benzodiazepines, steroids, plasmapheresis, and intravenous immunoglobulin (IVIG)

Reference:

• Dalakas MC. Stiff person syndrome: Advances in pathogenesis and therapeutic interventions. Curr Treat Options Neurol. 2009;11:102–110. doi: http://dx.doi.org/10.1007/s11940-009-0013-9.
• Lee Y et al. Association of stiff-person syndrome with autoimmune endocrine diseases.World J Clin Cases. 2019 Oct 6; 7(19): 2942–2952.