Anti‐aquaporin‐4 antibodies in the context of assorted immune‐mediated diseases

Background and purposes: Anti‐aquaporin 4 antibodies are specific markers for Devic‘s disease. This study aimed to test if this high specificity holds in the context of a large spectrum of systemic autoimmune and non‐autoimmune diseases. Methods: Anti‐aquaporin‐4 antibodies (NMO‐IgG) were determined by indirect immunofluorescence (IIF) on mouse cerebellum in 673 samples, as follows: group I (clinically defined Devic’s disease, n = 47); group II [inflammatory/demyelinating central nervous system (CNS) diseases, n = 41]; group III (systemic and organ‐specific autoimmune diseases, n = 250); group IV (chronic or acute viral diseases, n = 35); and group V (randomly selected samples from a general clinical laboratory, n = 300). Results: MNO‐IgG was present in 40/47 patients with classic Devic’s disease (85.1% sensitivity) and in 13/22 (59.1%) patients with disorders related to Devic’s disease. The latter 13 positive samples had diagnosis of longitudinally extensive transverse myelitis (n = 10) and isolated idiopathic optic neuritis (n = 3). One patient with multiple sclerosis and none of the remaining 602 samples with autoimmune and miscellaneous diseases presented NMO‐IgG (99.8% specificity). The autoimmune disease subset included five systemic lupus erythematosus individuals with isolated or combined optic neuritis and myelitis and four primary Sjögren’s syndrome (SS) patients with cranial/peripheral neuropathy. Conclusions: The available data clearly point to the high specificity of anti‐aquaporin‐4 antibodies for Devic’s disease and related syndromes also in the context of miscellaneous non‐neurologic autoimmune and non‐autoimmune disorders.