Neuromyelitis optica spectrum disorder presenting with concurrent autoimmune diseases.

Neuromyelitis optica spectrum disorder (NMOSD) is an autoimmune syndrome characterized by optic nerve and spinal cord inflammation. In recent years, there has been increasing awareness of NMOSD presenting concurrently with other autoimmune diseases, including myasthenia gravis (MG), systemic lupus erythematosus (SLE), Sjögren's syndrome, and sarcoidosis, among others. Whether these diseases coexist in patients due to shared susceptibility to multiple autoimmune conditions as a result of a genetic tendency toward humoral autoimmunity, or whether systemic rheumatologic diseases facilitate some aspect of NMOSD pathogenesis remains an open question. Here, we describe two cases of NMOSD presenting with concurrent autoimmune disease, and highlight the clinical features and diagnostic challenges of each case. Our first patient had aquaporin-4 antibody-positive NMOSD with concurrent hypothyroidism, SLE, and muscle specific kinase antibody-positive MG. Our second patient had seronegative NMOSD with concurrent acetylcholine receptor antibody-positive MG. Practitioners should be aware of the potential for patients to present with a combination of NMOSD and one or more concurrent autoimmune diseases to ensure timely diagnosis and appropriate treatment.