Autoimmune Epilepsy With Isolated Serum Positivity for Anti–Gamma‐Aminobutyric Acid Type A Receptor Antibodies: A Case Report

ABSTRACT A 67‐year‐old woman has experienced recurrent generalized seizures since 2022 and was admitted to our department on multiple occasions. No neurological deficits or cerebrospinal fluid (CSF) abnormalities were observed during the interictal periods. Brain MRI revealed multifocal, reversible cortical–subcortical FLAIR hyperintense lesions. Antiepileptic drugs were administered, and the patient has remained seizure‐free. Epilepsy due to an immune‐mediated mechanism was suspected. Anti‐gamma‐aminobutyric acid type A (GABA A ) receptor antibodies were identified in the serum but not in the CSF using a cell‐based assay. Although GABA A receptor antibodies are typically detectable in both serum and CSF, several reports have described cases with serum‐only positivity. Our case highlights that autoimmune epilepsy may present without overt encephalitic features and with isolated serum antibody positivity. Therefore, negative CSF results do not necessarily exclude antibody‐mediated disease, and concurrent testing of both serum and CSF is recommended in clinical practice.