Background/Purpose: Despite polymyalgia rheumatica (PMR) being the most common inflammatory rheumatic disease in those over the age of 50 years, there remains a significant unmet need for a reliable serum biomarker of disease activity, to aid the diagnosis, and the identification of disease relapse. The aim of this pilot study was to evaluate the levels of 7 serum cytokines in a cohort of newly diagnosed PMR patients.

Methods: 15 consecutive patients, who had active, untreated PMR were recruited from a fast track PMR clinic. Those with signs, symptoms or imaging confirmation of GCA were excluded. The following circulating cytokines were then measured using ELISA on participants serum: MCP-1(CCL2) , interleukin-6 (IL-6), CXCL9 (MIG), MIP-1 alpha (CCL3), Tumour necrosis factor alpha (TNF-a), interleukin-1 beta (IL-1b) and interleukin-17A (IL-17A). The statistical analysis was performed using STATA MP Version 18.

Results: A total of 15 patients with PMR were studied (33% female; 67% male). The mean age was 71.71 (SD 5.97). In reference to defined manufacturer parameters, at diagnosis serum MCP-1 levels were elevated in 14/15 (93%), with a median level of 732.5pg/ml (571, 921). Serum IL-6 levels were elevated in 10/15 (67%) with a median level of 11.85 pg/ml (6.05, 31.8). CXCL9 was elevated in 14/14 (100%), with a median level of 2184pg/ml (1180, 3897.5). Levels of MIP-1 alpha were elevated in 4/14 (28.6%) patients, with a median level of 91.1 pg/ml (76.5, 105). IL-1b was elevated in 2/15 (13.3%) with a median level of 0.445pg/ml (0.27, 0.815). TNF-a was elevated in 1/15 (6.7%) with a median level of 15.35pg/ml (12.85, 16.8). Finally, IL-17A was only available in 6 patients, with 5/6 (83%) demonstrating increased levels, with a median IL-17A level of 3.02 (2.89,3.27).

Conclusion: Our pilot study has demonstrated the potential utility of serum CXCL-9, MCP-1 and IL-17A in the diagnosis of those with isolated PMR. Our study offers the advantage of inclusion of an isolated PMR cohort, who are naïve to any treatment including steroid. Our findings provide promise for future large scale prospective studies exploring the role of these cytokines in PMR, which may also facilitate a deeper understanding of the inflammatory and immune mechanisms underlying PMR pathophysiology.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/cytokine-profile-of-newly-diagnosed-patients-with-isolated-polymyalgia-rheumatica/