Clinical Utility of YKL-40 in Polymyositis/dermatomyositis-associated Interstitial Lung Disease.

Interstitial lung disease (ILD) is involved in polymyositis/dermatomyositis (PM/DM), a disease associated with poor prognoses. Chitinase-3-like-1 protein (YKL-40) has pleiotropic biological activities involved in inflammation, cell proliferation, and tissue remodeling; however, the clinical application of YKL-40 remains limited. We investigated the clinical significance of YKL-40 in PM/DM-ILD. Sixty-nine consecutive patients with PM/DM-ILD and 34 healthy controls were analyzed. We measured baseline and followup serum YKL-40 using an ELISA, evaluated the association of YKL-40 with clinical variables and survival, and examined YKL-40 expression in lung specimens from patients with PM/DM-ILD using immunohistochemistry. Serum YKL-40 levels were significantly greater in patients with PM/DM-ILD compared with healthy controls (p < 0.0001). Serum YKL-40 was correlated with arterial oxygen pressure (r = -0.40, p < 0.001) and percent-predicted DLCO (r = -0.41, p = 0.01) in patients with PM/DM-ILD. Multivariate Cox hazard analysis demonstrated that higher serum YKL-40 and lower percent-predicted forced vital capacity were independently associated with a poor prognosis. Immunohistochemistry analysis demonstrated that YKL-40 expression was enhanced in aggregated intraalveolar macrophages and hyperproliferative alveolar epithelial cells in patients with PM/DM-ILD. YKL-40 is a promising biomarker for evaluating PM/DM-ILD activity/severity and predicting disease prognosis. Insights into YKL-40 might help elucidate the pathogenesis of PM/DM-ILD.