Background Recent studies have identified serum VGKC antibodies in various cohorts of patients with epilepsy, and have suggested a potential aetiological role for VGKC antibodies in epilepsy.

Methods We have undertaken systematic testing for VGKC antibodies in patients with otherwise unexplained adult onset epilepsy, seen at a regional neurosciences centre. Patients in whom VGKC antibodies were identified were given immunotherapy in addition to antiepileptic drugs (AED). Epilepsy classification and response to immunotherapy were analysed.

Results Of 128 patients tested, four had high titres of VGKC antibodies. Seizure semiology was suggestive of complex partial seizures of temporal origin in all patients. All patients had on going seizures in spite of treatment with AED. VGKC antibody levels at presentation ranged from 180 pM to 3450 pM. All patients were treated with high dose steroids and three patient subsequently received Azathioprine. In three patients, VGKC antibody titres fell after starting treatment with steroids, one patient required thymectomy for thymic hyperplasia. All patients experienced improvement in seizure control, and three have remained seizure free since commencing immunotherapy. One patient had CASPR2 antibodies, other three were negative for CASPR2 and LGI1 antibodies.

Conclusion Identifying patients with epilepsy and VGKC antibodies have significant therapeutic implications, as immunotherapy results in complete control of AED resistant seizures. The pathogenic antibody in patients with epilepsy may be directed to an as yet unidentified component of the VGKC receptor complex.