Aquaporin4-IgG seropositivity significantly increases the risk of comorbid autoimmune diseases in NMOSD patients: population-based registry data

Background The aim of our study was to estimate the frequency of autoimmune comorbidities, in NMOSD patients from the national Serbian NMOSD Registry. Methods Our study comprises 136 patients with NMOSD, diagnosed according to the NMOSD criteria 2015. At the time of the study, in the Registry were collected demographic and clinical data, including those related to the coexisting comorbidities and pathogenic autoantibodies. Not all patients were tested for all autoimmune antibodies. None of the seronegative aquaporin4-IgG (AQP4-IgG) NMOSD patients, included in the Registry, were positive for the myelin oligodendrocyte glycoprotein IgG. Results: Among 136 NMOSD patients, 50 (36.8%) had at least one associated autoimmune disorder. AQP4-IgG was present in the sera from 106 patients (77.9%), the proportion of NMOSD patients with autoimmune comorbidities being significantly higher in the AQP4-IgG positive subgroup in comparison to the AQP4-IgG negative ( p = 0.002). AQP4-IgG seropositive NMOSD patients had 5.2-fold higher risk of comorbid autoimmune diseases (OR = 5.2, 95% CI 1.4–18.5, p = 0.012). The most frequently reported diseases were autoimmune thyroid disease (15.4%), Sjogren’s syndrome (11.0%), systemic lupus erythematosus (5.1%), myasthenia gravis (4.4%), and primary antiphospholipid antibody syndrome (2.9%). Antinuclear antibodies (ANAs) were frequently detected in the subgroup of NMOSD patients tested for this antibody (50/92; 54.3%). The higher frequency of ANAs and anti-extractable nuclear antigen autoantibodies, in the subgroups of AQP4-IgG-positive patients compared to the AQP4-IgG negative, tested for these antibodies, was statistically significant ( p = 0.009, and p = 0.015, respectively). Conclusion In conclusion, based on our results, in a defined cohort with European ethnical background, a wide spectrum of autoimmune diseases is frequently associated with AQP4-IgG seropositive NMOSD patients.