Successful Treatment of Anti-Caspr2 Syndrome by Interleukin 6 Receptor Blockade Through Tocilizumab

IMPORTANCE A patient with a Caspr2 autoantibodies–associated syndrome had an unusual clinical triad and an excellent response to B-cell–anergizing therapy using the humanized monoclonal antibody tocilizumab directed against the interleukin 6 (IL-6) receptor. OBSERVATIONS A 55-year-old man had an atypical clinical triad of epilepsy, dysarthria, and paroxysmal kinesigenic dystonia, and a high titer of Caspr2 antibodies was detected in his serum and cerebrospinal fluid. Screening for underlying neoplasias was negative. With initial methylprednisolone sodium succinate and alternate treatment using plasma exchange and immunoabsorption as well as subsequent IL-6 receptor blockade through tocilizumab, a complete and stable remission of symptoms has been achieved throughout the follow-up period of 7 months. CONCLUSIONS AND RELEVANCE In our patient, the implementation of a B-cell–anergizing therapy using tocilizumab, a humanized monoclonal antibody against the IL-6 receptor, has shown an excellent response. Larger case series or even controlled studies are needed to confirm the efficacy of tocilizumab in autoimmune synaptic or presynaptic diseases.