Joint pain is common in subjects with IBD and is linked to several factors including SpA, drug therapy, concomitant OA or FM. The primary aim of this study was to estimate the prevalence of primary FM and concomitant FM and SpA in a cohort of patients with IBD utilizing clinical and US assessment.
A total of 301 consecutive cases with IBD attending two IBD Units were assessed by a rheumatologist for Assessment of SpondyloArthritis International Society criteria fulfilment for SpA or the 2010 ACR criteria for FM. Some 158 cases also had US entheseal examination on large insertions in the upper and lower limbs.
Thirty-seven IBD patients (12%) met the ACR criteria for primary FM with 9% presenting with primary FM and 3.3% presenting with concomitant FM and SpA. Meeting FM criteria was not related to smoking, sedentary job, BMI or the presence of psoriasis. FM patients presented higher Leeds Enthesitis Index, BASDAI and BASFI scores than SpA patients. At US examination, patients who satisfied the Assessment of SpondyloArthritis International Society criteria for SpA had significantly higher mean enthesis or patient power Doppler positive as compared with the IBD and FM group (P < 0.001).
We found that FM occurred in 12% of SpA patients and in this setting SpA disease activity indices performed poorly. US examination in a large patient subgroup showed a promising discriminating capacity between FM and SpA in IBD patients.