Objectives: Clinical features of primary Sjögren's syndrome (pSS) overlap with those of fibromyalgia (FM). This cross-sectional study was conducted to investigate the prevalence of FM in pSS patients and to compare the clinical features of pSS patients with FM to those without FM.
Methods: One hundred pSS patients were consecutively assessed to identify the presence of FM according to the American College of Rheumatology (ACR) 2010 criteria. Clinical and laboratory data were collected from all patients. Additional assessments included EULAR Sjögren's Syndrome Patient Reported Index (ESSPRI) and EULAR Sjögren's Syndrome Disease Activity Index (ESSDAI). The severity of depression was measured by Hamilton depression rating scale 17-items (HAM-D scale).
Results: The prevalence of FM was 31.0% (31/100) in pSS. Widespread pain index and symptom severity scale were significantly correlated with ESSPRI (r=0.6542 and r=0.7173, both p<0.0001) and HAM-D scale (r=0.6734 and r=0.6471, both p<0.0001) in pSS. In multivariate analysis, ESSPRI and HAM-D scale were independently associated with increase of tender point count and symptom severity scale. ESSPRI was significantly higher in pSS patients with FM compared to those without FM (p<0.0001). The prevalence of FM in pSS patients with moderate-to-severe depression was significantly higher than those with mild depression or without depression (odds ratio= 10.62, p=0.0009). Serum 25-hydroxy vitamin D3 levels in pSS patients with FM were significantly (p=0.0072) decreased compared to those without FM.
Conclusions: Our study showed that FM was prevalent in pSS. FM was associated with higher ESSPRI and more severe depression.