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


  • 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)


Last edited 04/2021 and last reviewed 04/2021