Approximately 20% of patients with epilepsy have a co-occurring autoimmune disorder, and autoantibodies directed against the smaller isoform of glutamate decarboxylase (GAD65Ab) have been found in patients with epilepsy, as well as in patients with stiff person syndrome (SPS, a rare disorder characterized by fluctuating muscle rigidity and heightened sensitivity to stimuli) and type 1 diabetes (T1D). The fact that epilepsy is 4- to 6-fold more prevalent among patients with T1D than the general population has led researchers to investigate the possible role of these GAD65Ab in these diseases.
Researchers, reporting findings in the Orphanet Journal of Rare Diseases, collected sera from patients with autoimmune epilepsy (n = 38) from the T1D Exchange program at 3 centers in Finland, France, and the United States. Ten of these patients also had T1D. Sera from 42 patients with T1D who did not have other autoimmune disorders and sera from 20 patients with SPS were also collected.
They also concluded that patients who are diagnosed with both type 1 diabetes and epilepsy may present 2 different epileptic etiologies; in the former group, type 1 diabetes may co-occur with nonautoimmune epilepsy, and the latter group may have an underlying autoimmune component that contributes to the epileptic condition. Patients who fall into this second group, suggest the authors, may benefit from immunotherapy even if they do not respond well to conventional antiepileptic drugs.