IndicationSuspicion of paraneoplastic syndromes particularly in autoimmune encephalitis.MethodIndirect immunofluorescence (IIF) using transfected cells.AnswerThe result is reported as positive or negative. A positive result is followed by a titer (serum).InterpretationLGI-1 is a subunit in the potassium channel complex (VGKC). Antibodies against LGI-1 have been reported in classical autoimmune encephalitis and epilepsy. Antibodies against LGI-1 are the second most common in autoimmune encephalitis following antibodies against NMDAR. Antibodies against LG-1 are detected more often in men, age when diagnosed has varied between 30-80 years (median 60 years). LGI-1 antibodies are associated with tumors (lung, thymoma but also other tumor forms) in 25-31% of the cases.
The LGI-1 belongs to the group of extracellular antigens. Generally, immunotherapy is more often effective in autoantibodies directed against extracellular antigens than in autoantibodies against intracellular antigens. Antibody titers can be used to monitor treatment effectiveness. Screening for cancer diagnosis is recommended.
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