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September 2016

Contactin-Associated Protein-like 2 Antibodies: Tackling the Issue of Syndrome Diversity

Author Affiliations
  • 1Epilepsy Centre Bethel, Krankenhaus Mara, Bielefeld, Germany
JAMA Neurol. 2016;73(9):1058-1059. doi:10.1001/jamaneurol.2016.1739

In 2007, the detection of IgG antibodies against the N-methyl-d-aspartate receptor in young women with encephalopathy opened a new field in neurology: the study of encephalitides with antibodies directed against well-defined antigens on the surfaces of central nervous system neurons.1 In 2010, the Oxford Neuroimmunology Group detected contactin-associated protein-like 2 (CASPR2) antibodies as one of the next antigenic targets of presumably pathogenic IgG antibodies.2 Unlike the N-methyl-d-aspartate receptor and most of the other antigens on neural surfaces, CASPR2 is not a receptor but associates with voltage-gated potassium channels at the juxtaparanodes of myelinated axons. Together with TAG-1, CASPR2 forms a scaffold beneath the myelin sheath, which enables a clustering of those channels. This is required for the proper electrical function of the neurons.3 Until recently, to my knowledge, no more than 50 patients with CASPR2 antibody–associated syndromes were reported in dedicated series.2,4-6 Patients were diagnosed as having limbic encephalitis (LE), peripheral nerve hyperexcitability (neuromyotonia), a combination of central nervous system symptoms and neuromyotonia (Morvan syndrome), or ataxia.

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