626 hospitalized patients with SLE or SS were retrospectively studied, and sera from 6 patients with suspected NMOSDs and SLE (3) or SS (3) were evaluated. As a result, 2 patients’ (1 with SLE and 1 with SS) sera samples were positive for AQP4-IgG. The gene discussed is AQP4; the disease is systemic lupus erythematosus.