Disentangling fibromyalgia from spondyloarthopathy in the patient with inflammatory bowel disease

Abstract Background Joint pain is common in subjects affected by Inflammatory bowel disease (IBD) and is linked to several factors including spondyloarthritis (SpA), drug therapy, concomitant osteoarthritis and fibromyalgia (FM). The primary aim of this study was to estimate the prevalence of primary FM and concomitant FM and SpA in a cohort of IBD patients. The secondary aim was to assess the impact of FM on clinimetric scores and ultrasonographic features. Methods Consecutive cases with IBD attending two IBD Units were assessed by a rheumatologist for ASAS criteria for SpA or the 2010 ACR criteria for FM. The rheumatological assessment included a 66 swollen joint count (SJC) and 68 tender joint count (TJC), Maastricht Ankylosing Spondylitis Score (MASES), Leeds Enthesitis Index (LEI) and the FM tender points examination, the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) and Bath Ankylosing Spondylitis Functional Index (BASFI). One hundred and fifty-eight patients seen at Reggio Emilia centre underwent US entheseal examination. MRI and HLA-B27 determination were requested if needed for diagnostic confirmation. Results 301 patients were enrolled with 148 completing the clinical and imaging/laboratory assessment if requested for diagnostic purpose. A total of 37 IBD patients (12%) met the ACR criteria for FM: 27 patients (9%) presented the criteria for primary FM and 10 patients (3.3%) presented FM and SpA. Patients who met FM criteria were mostly female (81%, p < 0.001), slightly older, with longer duration of disease; no correlation with smoking, sedentary job, body mass index (BMI) or psoriasis. Of note FM patients presented higher LEI, BASDAI and BASFI scores than SpA patients. At US examination patients who satisfied ASAS criteria for SpA had significantly higher mean enthesis/patient PD positive as compared with IBD and FM group (p < 0.001 for the two comparison) and had more patients with at least one PD positive enthesis (p < 0.001 and p = 0.028 respectively). Acute entheseal lesions had a higher prevalence in the ASAS+ group as compared with the other two groups (p = 0.002 vs. IBD group and p = 0.009 vs. FM group). Chronic entheseal lesions had the same prevalence in the three groups of patients. Conclusion FM is common among IBD patients and more prevalent in females and patients aged ≥ 45 years old. In this subgroup of patients SpA disease activity indices performed poorly for distinguishing patients with disease activity from those with functional impairment. On the contrary, US examination showed a promising discriminating capacity in SpA patients.