LGI1 and CASPR2 (Anti- voltage gated potassium channel associated proteins)
Antibodies against the VGKC associated proteins LGI1 and Caspr2 are associated with a number of neurological syndromes.
Anti-LGI1 antibody encephalitis usually manifests in a number of ways. It can cause faciobrachial dystonic seizures (FBDS), other focal seizures - often with prominent autonomic features - a more pronounced limbic encephalitis with amnesia, cognitive decline and seizures, or it can cause a rapidly progressive encephalopathy (Pubmed ID 27590293).
Anti-Caspr2 antibody mediated syndromes include peripheral nerve hyperexcitability, Morvan syndrome and a more protracted, subacute limbic encephalitis with encephalopathy, seizures, cerebellar dysfunction, autonomic disturbance, neuropathic pain, insomnia and weight loss (Pubmed ID 27371488).
Antibodies against Caspr2 or LGI1 are identified in our laboratory via indirect immunofluroscence of cell lines transfected with cDNA coding the protein of interest. This is a very specific and sensitive test for antibodies against these antigens and an alternative to the anti-voltage-gated potassium channel complex antibody (VGKCC) radioimmunoassay.