Analysis index

0,5 ml serum

< 72 pmol/l

Autoimmune encephalitis, neuromyotonia

VGKC-complex antibodies were described between 1995 and 2001 in various clinical syndromes, such as limbic encephalitis, Morvan syndrome or neuromyotonia. Over the past few years, however, it was found that the “VGKC-complex” comprises at least three antigens, the antibodies which have different clinical meaning:
Antibodies against LGI1
Antibodies against CASPR2
Antibodies against other antigens, e.g. contactin-2
Antibodies against LGI1 and CASPR2 bind to extracellular domains of potassium-channel-associated proteins and are therefore typical antibodies against surface antigens. They have pathogenic relevance and correlate with specific clinical pictures. LGI1 – Limbic encephalitis, FBDS, hyponatremia CASPR2 – Limbic encephalitis, neuromyotonia, Morvan syndrome, neuropathic pain
LGI1 and CASPR2-associated syndromes respond well to immunotherapy. CASPR2 antibodies can be associated with tumors (thymomas).
In contrast, VGKC-complex antibodies not directed against LGI1 and CASPR2 have no clinical relevance in the initial diagnostics. These antibodies are often directed against intracellular components of the VGKC-complex or even against the 125J-α-dendrotoxin used for marking of VGKC-complexes in the test. They are associated with heterogenic clinical syndromes, without definite indication of an autoimmune etiology and can also be found in 5 % of control persons (1).
Testing for VGKC-complex antibodies is also not suitable as a sole screening test for the demonstration of LGI1 or CASPR2 antibodies, as this method is not sensitive enough. Low-titer LGI1 and CASPR2 results are not captured (2).
The diagnostics for LGI1 antibodies and CASPR2 antibodies are part of the “standard program” for neural antibodies at Laboratory Krone.
Literature:
1. Lang B, et al. J Neurol Neurosurg Psychiatry. 2017 Apr;88(4):353-361
2. van Sonderen et al., Neurology. 2016 May 3; 86:1692-1699