Semiquantitative measurement of aquaporin-4 antibodies as a possible surrogate marker of neuromyelitis optica spectrum disorders with systemic autoimmune diseases.

Objectives: To assess the association between serum aquaporin-4 (AQP4) autoantibodies and neuromyelitis optica spectrum disorders (NMOSDs) associated with systemic autoimmune diseases. Methods: We retrospectively studied 626 hospitalized patients with systemic lupus erythematosus (SLE) or Sjögren's syndrome (SS). We collected serum samples from those patients with suspected NMOSDs (i.e., myelitis or optic neuritis) at the time of onset and thereafter. AQP4 antibodies were measured by a cell-based indirect immunofluorescence assay using AQP4-transfected HEK-293 cells in a semi-quantitative manner. Results: Sera from 6 patients with suspected NMOSDs and SLE ( n = 3) or SS ( n = 3) were evaluated. Among these, 2 patients' sera samples, i.e., 1 with SLE and 1 with SS, were positive for AQP4 antibodies. There was an inverse relationship between disease amelioration and antibody titer in one NMOSD patient, whereas the antibody titer remained high in the other NMOSD patient, whose clinical manifestations of NMOSDs did not improve despite intensive immunosuppressive treatments. Conclusions: These results indicate that serum AQP4 antibodies are present in some SLE/SS patients with myelitis/optic neuritis and might be associated with clinical outcomes. The semi-quantitative measurement of the AQP4 antibody might be a possible surrogate marker in patients with NMOSDs associated with systemic autoimmune diseases. [ABSTRACT FROM AUTHOR]