Limbic encephalitis associated with anti-voltage-gated potassium channel complex antibodies mimicking Creutzfeldt-Jakob disease.

IMPORTANCE: Limbic encephalitis that is associated with anti-voltage-gated potassium channel complex (VGKCC) antibodies (VGKCC syndrome) is an autoimmune, usually nonparaneoplastic form of encephalitis that is responsive to immunotherapy. Differentiating this treatable disease from others that have a similar presentation is thus important. OBSERVATIONS: We present the case of a 58-year-old man who had a rapid onset of progressive confusion, twitching of the face and hand, and abnormal basal ganglia detected by magnetic resonance imaging. His conditions were initially diagnosed as Creutzfeldt-Jakob disease (CJD). Faciobrachial dystonic seizures, possibly pathognomonic for the VGKCC syndrome, had been misdiagnosed as myoclonus. Treatment led to a complete resolution of his symptoms. CONCLUSIONS AND RELEVANCE: Given the similarities of the clinical features and, at times, the neuroimaging findings of VGKCC syndrome to CJD, recognizing VGKCC syndrome and the highly associated and distinctive faciobrachial dystonic seizures is very important. Because this syndrome is the most common treatable condition that mimics CJD, we believe that it is crucial to screen all patients with presumed CJD for this reversible condition.