Plasma heat shock protein 90 levels in patients with spondyloarthritis and their relation to structural changes: a cross-sectional study.

Aim: Heat shock protein 90 (Hsp90) is a molecular chaperone regulating immune response. We aimed to assess systemic Hsp90 as a biomarker for spondyloarthritis (SpA). Materials & methods: Total of 80 axial SpA (axSpA) and 22 psoriatic arthritis patients and a corresponding number of age- and sex-matched healthy controls (HC) were included. Plasma Hsp90 levels were measured by ELISA. Results: Hsp90 was significantly increased in axSpA patients compared with HC (median interquartile range: 15.7 [10.5-19.8] vs 8.3 [6.6-11.8] ng/ml, p < 0.001). Moreover, Hsp90 was superior to C-reactive protein in differentiating axSpA (and both radiographic axSpA [r-axSpA] and nonradiographic-axSpA) from HC. Hsp90 levels correlated with bone marrow edema of sacroiliac joints in r-axSpA patients (r = 0.594, p = 0.019). Conclusion: Hsp90 could become a biomarker for active inflammation in r-axSpA, and can better distinguish axSpA patients from healthy subjects than C-reactive protein.