Interferon causes no myasthenia in a seropositive patient with multiple sclerosis

We describe a successful outcome of long-term interferon β-1b therapy in a patient who had multiple sclerosis (MS) with positive serum autoantibody to muscle acetylcholine receptor (AChR-Ab). Because of the reported possible causative linkage between interferon β-1b and myasthenia gravis (MG), the presence of the pathogenic antibody complicated therapeutic strategies. We carefully observed the patient for further 6 months before the treatment, excluding symptomatic MG. The interferon β-1b therapy then provided a clinical benefit. Hopefully this report will allow MS patients in similar situations to make more rapid, unprejudiced judgments than our patients.