Which disorders are associated with stiff person syndrome?

Updated: Jun 14, 2018
  • Author: Nancy Theresa Rodgers-Neame, MD; Chief Editor: Nicholas Lorenzo, MD, MHA, CPE  more...
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Diabetes mellitus: Although different epitopes for the GAD antibodies in diabetes have been identified, stiff person syndrome and diabetes have demonstrated comorbidity. This comorbidity occurs in association with a finding of positive GAD antibodies. Early distal involvement and involvement of a single limb is more frequent in patients with diabetes mellitus. Stiff person syndrome has also been associated with diabetes mellitus and ICA 105 pancreatic autoantigen with and without the presence of anti-GAD antibodies. About 35 percent of SPS patients have type 1 diabetes. [33]

Thyroiditis: An association with thyroiditis has been described. This may be due to comorbidity of multiple autoimmune entities or may be a more direct association. At least one group has suggested a link due to neuromuscular hyperactivity.

Breast cancer: A variant of stiff person syndrome occurs rarely in patients with breast cancer. The antibodies involved are to a synaptic protein, amphiphysin. Anti-GAD antibodies are absent.

Epilepsy: Anti-GAD antibodies have been described in patients with medication-resistant focal epilepsies. In one series, 4 of 19 patients with anti-GAD–positive stiff person syndrome were also found to have localization-related epilepsy.

Cerebellar ataxia: A number of case studies report the presence of cerebellar ataxia (with or without stiff person syndrome) associated with anti-GAD antibodies.

A form of familial spastic cerebral palsy has been described with a missense mutation in the GAD-67 gene. This is a different isoform of glutamic decarboxylase; however, it demonstrates that the pathophysiology of stiff person syndrome is likely due to abnormalities in the function of glutamic acid decarboxylase.

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