Fibromyalgia is a common comorbidity that occurs with enthesitis in both men and women with spondyloarthritis (SpA), and is associated with worse SpA disease severity scores, according to study findings published in Joint Bone Spine.

Researchers analyzed data from the Assessment of Spondyloarthritis International Society Peripheral Involvement in SpA (PerSpA) study, which included patients from 24 countries recruited between July 2018 and February 2020 with a diagnosis of axial SpA (radiographic and nonradiographic), peripheral SpA, or psoriatic arthritis (PsA). Enthesitis was defined as ever having enthesitis. Fibromyalgia was determined with a clinical diagnosis or a fibromyalgia rapid screening test (FiRST) score of at least 5 out of 6.

 A total of 4465 patients were included in the study. Of these, 1984 (44.4%) had enthesitis, 775 (17.4%) had fibromyalgia based on the FiRST questionnaire, and 400 (9%) had a clinical diagnosis of fibromyalgia. Enthesitis and fibromyalgia co-occurred in 425 (10.3%) of patients using the FiRST criteria and 238 (5.3%) patients using a clinical diagnosis of fibromyalgia.


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Enthesitis and fibromyalgia co-occurrence (EFM) was more common in women compared with men when fibromyalgia was defined clinically (76.9% vs 23.1%) and when using FiRST criteria (62.6% vs 37.4%). Disease severity scores were significantly higher in patients with EFM compared with SpA or SpA plus enthesitis, regardless of sex or whether the FiRST questionnaire or clinical diagnosis was used. Factors significantly associated with ESM in multivariable analyses (using fibromyalgia defined by clinical diagnosis or FiRST criteria) include female sex and Bath ankylosing disease activity index (BASDAI) score.

Limitations of the study included the cross-sectional nature of the data and challenges in diagnosing fibromyalgia both clinically and using the FiRST questionnaire. 

The study authors concluded, “The presence of [fibromyalgia] inflates disease severity measures in individuals with enthesitis, with no sex effect demonstrated. It remains unknown whether the presence of [fibromyalgia] in individuals with enthesitis leads to over-treatment of SpA. Further sex-stratified studies are required to validate the FiRST questionnaire in individuals with enthesitis, further delineate the role of imaging in coexistent [fibromyalgia] and enthesitis, and develop holistic management strategies.”

Reference

Fitzgerald GE, Maguire S, Lopez-Medina C, Dougados M, O’Shea D, Haroon N. Tender to touch–Prevalence and impact of concomitant fibromyalgia and enthesitis in spondyloarthritis: An ancillary analysis of the ASAS PerSpA study. Joint Bone Spine. Published online May 27, 2022. doi:10.1016/j.jbspin.2022.105420