Presence of voltage-gated potassium channel complex antibody in a case of genetic prion disease

Voltage-gated potassium channel (VGKC) complex antibody-mediated encephalitis is a recently recognised entity which has been reported to mimic the clinical presentation of Creutzfeldt-Jakob disease (CJD). Testing for the presence of this neuronal surface autoantibody in patients presenting with subacute encephalopathy is therefore crucial as it may both revoke the bleak diagnosis of prion disease and allow institution of potentially life-saving immunotherapy. Tempering this optimistic view is the rare instance when a positive VGKC complex antibody titre occurs in a definite case of prion disease. We present a pathologically and genetically confirmed case of CJD with elevated serum VGKC complex antibody titres. This case highlights the importance of interpreting the result of a positive VGKC complex antibody with caution and in the context of the overall clinical manifestation.