Anti-N-methyl-D-aspartate receptor antibodies are associated with fibromyalgia in patients with systemic lupus erythematosus: a case-control study

Objective. The high concordance between systemic lupus erythematosus (SLE) and fibromyalgia (FM) suggests common underlying mechanisms related to pain and distress in both patient groups. Increasing evidence indicates that N-methyl-D-aspartate receptors (NMDARs) play a major role in the induction and maintenance of central sensitisation with chronic pain. In this study, we evaluated the role of anti-NMDAR antibodies in the development of FM in patients with SLE. Methods. Sera from 104 patients with SLE, 112 patients with FM, and 110 healthy controls were analysed to detect antibodies to the N-terminus of the 2B subunit of NMDARs (GluN2B). Subjects underwent clinical examination and neuropsychiatric evaluation, and completed a questionnaire regarding FM and neuropsychiatric symptoms. Results. Of the 104 patients with SLE, 18 (17.3%) had FM. The anti-GluN2B antibody titre was significantly higher in patients with SLE (p<0.001). Among patients with SLE, those with concomitant FM had higher anti-GluN2B antibody titres (p<0.05). The anti-GluN2B antibody titre was associated positively with the tender point count (p=0.016) and the widespread pain index (p=0.005), but not with other symptom measurements. Anti-GluN2B antibody-positive patients with SLE were more likely to have neuropsychiatric systemic lupus erythematosus (NPSLE) and concomitant FM (p<0.05). Multivariate analysis showed that the anti-GluN2B antibody was an independent predictor of concomitant FM and NPSLE. Conclusion. To our knowledge, this report is the first to suggest that anti-NMDAR antibodies are associated with the pathogenesis of FM with SLE.