Objectives The high concordance of systemic lupus erythematosus (SLE) with fibromyalgia (FM) suggests common underlying mechanisms related to pain and distress in both patient groups. This study was aimed to evaluate roles of NMDAR antibodies in development of FM in SLE patients

Methods Sera from 104 SLE patients, 112 FM patients, and 110 healthy controls were analyzed to detect titers of antibodies to N-terminus of 2B subunit of NMDAR (GluN2B). Clinical, laboratory data and concomitant diseases were found by reviewing the patient charts. We underwent clinical examination and neuropsychiatric evaluation, and interviewed SLE patients using a structured questionnaire that included FM and neuropsychiatric symptoms.

Results 18 patients (17.3%) of total 104 SLE patients were revealed having FM. The titer of anti-GluN2B antibodies was significantly higher in SLE patients than FM patients and healthy controls (P <0.001). In SLE patients, patients with concomitant FM showed higher titers of anti-GluN2B antibodies (P <0.05). The titers of anti-GluN2B antibodies were correlated with tender point count (Spearman's rho =0.238, P=0.016) and widespread pain index (Spearman's rho =0.276, P=0.005), but not with other symptom scales. Anti-GluN2B antibody-positive SLE patients were more likely to have NPSLE and concomitant FM (P<0.05). In multivariate analysis, Anti-GluN2B antibody was independent predictor of concomitant FM and NPSLE.

Conclusions This is the first study to present that antibodies to NMDAR may be associated with pathogenesis of FM in SLE patients.

Disclosure of Interest None declared