Coexistence of myasthenia gravis and serological markers of neurological autoimmunity in neuromyelitis optica.

We systematically evaluated the frequency of neurological disorders and muscle and neural autoantibodies in 177 patients with neuromyelitis optica (NMO) and in 250 control subjects (173 healthy; 77 multiple sclerosis, MS, patients). An excess of myasthenia gravis (MG, 2%), and muscle-type acetylcholine receptor antibody (11%) was detected among NMO patients. The presence of neural or muscle autoantibodies was more common in NMO patients (34%) than in MS patients or healthy controls (7%), P < 0.0001. The coexistence of NMO and MG should be considered in atypical or refractory presentations of either disorder.