Autoimmunity reflects an altered immune status. The coexistence of three or more autoimmune diseases in a patient constitutes multiple autoimmune syndrome. Here, an interesting case with a history of Hashimoto's thyroiditis and got the diagnosis of systemic lupus erythematosus during her evaluation, in which the clinical signs of neuromyelitis optica spectrum disorder (NMOSD) and miyasthenia gravis cooccurred will be discussed. In addition to high-dose pulse steroid, plasmapheresis and intravenous immunoglobulin treatments, rituximab treatment was started and the patient is followed up without clinical worsening and disability in the three-year follow-up. Patients with diagnosis of NMOSD need special attention as multiple immune-mediated disorders may be present simultaneously or sequentially during the course of the disease process. This case report emphasizes the importance of a multidisciplinary team approach for a better understanding of disorders related to the breakdown of immune tolerance.