PT - JOURNAL ARTICLE AU - Michael Sweeney AU - Jonathan Galli AU - Scott McNally AU - Anne Tebo AU - Thomas Haven AU - Perla Thulin AU - Stacey L Clardy TI - Delayed LGI1 seropositivity in voltage-gated potassium channel (VGKC)-complex antibody limbic encephalitis AID - 10.1136/bcr-2016-218893 DP - 2017 Apr 11 TA - BMJ Case Reports PG - bcr2016218893 VI - 2017 4099 - http://casereports.bmj.com/content/2017/bcr-2016-218893.short 4100 - http://casereports.bmj.com/content/2017/bcr-2016-218893.full AB - We utilise a clinical case to highlight why exclusion of voltage-gated potassium channel (VGKC)-complex autoantibody testing in serological evaluation of patients may delay or miss the diagnosis. A 68-year-old man presented with increasing involuntary movements consistent with faciobrachial dystonic seizures (FBDS). Initial evaluation demonstrated VGKC antibody seropositivity with leucine-rich glioma-inactivated 1 (LGI1) and contactin-associated protein-like 2 (CASPR2) seronegativity. Aggressive immunotherapy with methylprednisolone and plasmapheresis was started early in the course of his presentation. Following treatment with immunotherapy, the patient demonstrated clinical improvement. Repeat serum evaluation 4 months posthospitalisation remained seropositive for VGKC-complex antibodies, with development of LGI1 autoantibody seropositivity. VGKC-complex and LGI1 antibodies remained positive 12 months posthospitalisation. Our findings suggest that clinical symptoms can predate the detection of the antibody. We conclude that when suspicion for autoimmune encephalitis is high in the setting of VGKC autoantibody positivity, regardless of LGI1 or CASPR2 seropositivity, early immunotherapy and repeat testing should be considered.