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Home > About Ataxia > Sporadic (non-hereditary) ataxia > Anti-glutamic acid decarboxylase (GAD) antibodies.
Background Stiff-person syndrome (SPS) is an immune-mediated central nervous system disorder characterized by fluctuating muscle stiffness, disabling spasms, and heightened sensitivity to external stimuli. Up to 80% of patients with SPS have anti–glutamic acid decarboxylase (GAD) antibodies in the serum or cerebral spinal fluid (CSF). Whether these antibodies are clinically relevant and correlate with disease severity is unknown.
It was first described in 1956 by Moersch and Woltman  as “stiff man syndrome. ” As women are more frequently affected, the disorder was subsequently named stiff person syndrome (SPS). Solimena et al. demonstrated the autoimmune nature of the disorder by identifying anti-glutamic acid decarboxylase (GAD) antibodies.