GABA Type B Receptor Antibody
Antibody targeting the B1 subunit of the gamma-aminobutyric acid-type B (GABA-B) receptor has been reported in patients with limbic encephalitis characterized by psychiatric symptoms and prominent seizures. Approximately 50% of antibody positive patients have small cell lung carcinoma (SLCL). Men and women are affected equally. The mean age of onset is 60 years.
Patients usually present with seizures, memory loss, mood changes, personality changes, psychosis, delirium or sleep disorders. The likelihood of an autoimmune etiology is increased if a patient has a history of autoimmune disorders, cancer, or cancer risk factors such as smoking.
Patients with GABA-B-R receptor antibodies may have other coexisting antibodies such as N type calcium channel antibody, GAD65 antibody, thyroid antibodies, and GNA/SOX 1 antibody
Antibody can be detected in both serum and CSF. If antibody is detected in serum, subsequent testing of CSF adds little value. However, patients with negative serum results sometimes have positive CSF results. High titer antibodies are more specific for limbic encephalitis.
GABA-B receptor antibody is detected using immunofluoresence to detect IgG binding to human cells transfected with B1 subunit of the GABA type B receptor. Transfected cells over-express the cognate protein, increasing sensitivity of the test. Specimen requirements are a red top tube of blood for serum antibody and 1 mL of CSF in a sterile vial for CSF antibody.
Reference value is no antibody detected.
