SPS is 1) frequently misdiagnosed due to multifaceted presentations and asymmetric signs, 2) disabling if untreated, and 3) associated with other autoimmune conditions.

Intravenous immune globulin is a well-tolerated and effective, albeit costly, therapy for patients with stiff-person syndrome and anti-GAD65 antibodies.

In patients with SPS, there is marked intrathecal antibody response against neuronal GAD(65) epitopes, indicating a clonal B cell activation in the CNS. Anti-GAD(65) antibodies at high titers, when confirmed with immunoblots, are highly specific for SPS and appear to impair GABA synthesis.

IVIg combined with prednisone for a 3-month period was not effective in IBM. Endomysial inflammation was significantly reduced after treatment, but the reduction was not of clinical significance.