GABAB receptor autoantibody frequency in service serologic evaluation

Area of Science:

• Neurology
• Immunology
• Oncology

Background:

• Small-cell lung carcinoma (SCLC) and limbic encephalitis are known to be associated with gamma-aminobutyric acid-B receptor (GABABR) autoantibodies.
• Diagnostic serology plays a crucial role in identifying these autoimmune accompaniments.

Purpose of the Study:

• To determine the frequency of GABABR-immunoglobulin G (IgG) in a diagnostic serology laboratory.
• To investigate the associated neurologic, oncologic, and serologic findings in patients with GABABR-IgG.

Main Methods:

• Indirect immunofluorescence on mouse brain tissue and transfected HEK293 cells were used to test serum and CSF specimens for GABABR-IgG.
• Three patient groups were analyzed: suspected autoimmune encephalopathy (n=3,989), unclassified CNS synaptic IgG (n=49), and SCLC-predictive autoantibodies (n=384).

Main Results:

• GABABR-specific IgG was detected in 17 patients (0.2% to 10% across groups).
• Limbic encephalitis and SCLC were common in seropositive patients, particularly in the suspected autoimmune encephalopathy group.
• N-type calcium channel antibody coexisted in seropositive patients from groups 1 and 2. Diverse neurologic presentations in group 3 were linked to coexisting T-cell-mediated autoimmunity.

Conclusions:

• GABABR autoantibody signifies an uncommon but treatable paraneoplastic neurologic disorder.
• The presence of GABABR autoantibody is typically associated with limbic encephalitis and SCLC.
• Early diagnosis and immunotherapy can lead to neurological improvement.