Rituximab treatment of stiff-person syndrome in a patient with thymoma, diabetes mellitus and autoimmune thyroiditis.

Stiff-person syndrome (SPS) is an autoimmune neurological disorder characterized by stiffness of the skeletal muscle with superimposed spasms and production of autoantibodies to glutamic acid decarboxylase (GAD) and amphiphysin. The disorder results from B cell-mediated clonal production of autoantibodies, requiring treatment with immunosuppressors; however, treatment results have been somewhat inconsistent. We report the results of rituximab treatment in a patient with SPS associated with a thymoma, diabetes mellitus, autoimmune thyroiditis and the presence of anti-GAD and anti-amphiphysin autoantibodies. The patient experienced a partial improvement following a thymectomy and the administration of prednisone, intravenous immunoglobulins and mycophenolate mofetil. Treatment with rituximab was followed by a complete sustained remission and the disappearance of serum anti-amphiphysin antibodies.