Insights from LGI1 and CASPR2 potassium channel complex autoantibody subtyping

Area of Science:

• Neuroimmunology
• Autoimmune Neurology
• Neurological Disorders

Background:

• Autoantibodies targeting the neuronal voltage-gated potassium channel (VGKC) complex are associated with various neurological conditions.
• Leucine-rich glioma-inactivated protein 1 (LGI1) and contactin-associated protein-like 2 (CASPR2) are identified as major antigenic targets within the VGKC complex.

Purpose of the Study:

• To investigate the clinical presentations associated with VGKC complex autoantibodies.
• To determine the frequency of LGI1 and CASPR2 autoantibodies in seropositive patients.
• To explore the relationship between antibody titers and specific neurological phenotypes.

Main Methods:

• Retrospective cohort study analyzing data from a large patient cohort (54,853 patients).
• Serologic evaluation for VGKC complex IgG, LGI1 IgG, and CASPR2 IgG.
• Clinical correlation of serologic findings with neurological symptoms and presentations.

Main Results:

• Of 54,853 patients, 1992 (4%) were positive for VGKC complex IgG.
• Among 316 clinically evaluated seropositive patients, 82 (26%) had LGI1 IgG and/or CASPR2 IgG.
• LGI1 IgG was associated with cortical presentations (cognitive impairment, seizures), while CASPR2 IgG was linked to peripheral motor excitability. Neither antibody was pathognomonic for a specific presentation.

Conclusions:

• Diverse and overlapping neurological phenotypes are observed across varying VGKC complex IgG values and LGI1/CASPR2 specificities.
• The presence of LGI1 IgG and CASPR2 IgG in samples with low and medium VGKC complex IgG values underscores the clinical relevance of these lower titers.
• Further research is needed to identify additional antigenic components of the VGKC macromolecular complex.