Objective: To investigate the behavior of serum YKL-40 in a cohort of patients with systemic sclerosis (SSc).
Methods: Forty SSc patients (35 women, 5 men) were investigated for serum YKL-40, soluble interleukin 2 receptor alpha (sIL-2Ra; by ELISA), von Willebrand factor (vWF; ELISA), and aminoterminal propeptide of type III procollagen (PIIINP; radioimmunoassay) concentrations. Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) were evaluated. Skin and organ system involvement were scored according to the Medsger organ/system severity scale.
Results: Serum YKL-40 in SSc patients (mean 132.9 ng/ml; median 75.5, 95% CI 87.8-175) was significantly higher than in controls (mean 66.6 ng/ml; median 52, 95% CI 54.6-78.6). Fourteen patients had levels > 135 ng/ml (cutoff value) with a mean of 264.7 +/- 160 ng/ml. Serum YKL-40 values were found to be more frequently increased in patients with arthralgias/arthritis (18 cases) than in patients without such features (4/22) (p = 0.021). Significant differences were found comparing serum YKL-40 concentrations in the patients with or without joint involvement (median 138 vs 57.5 ng/ml, respectively; p = 0.007). Serum YKL-40 levels correlated with the joint involvement severity score (p = 0.018) and sIL-2Ra levels (p < 0.001). No differences were found with any therapeutic regimen.
Conclusion: This preliminary study shows that YKL-40 serum levels are increased in SSc and that they are correlated with sIL-2Ra and joint involvement, suggesting a relationship with cartilage and/or fibroblast activity.