Serum YKL-40 level is associated with severity of interstitial lung disease and poor prognosis in dermatomyositis with anti-MDA5 antibody.

Objective: We aimed to investigate the clinical value of checking serum chitinase-3-like-1 protein (YKL-40) levels in anti-MDA5 antibody-positive dermatomyositis (anti-MDA5 + DM) patients.

Methods: One hundred and five consecutive anti-MDA5 + DM patients and 44 healthy controls were enrolled in this study. Baseline and follow-up serum YKL-40 were detected by ELISA. We evaluated the association of YKL-40 with rapidly progressive interstitial lung disease (RPILD), severity of interstitial lung disease (ILD), and ILD-related survival.

Results: Forty-one out of 105 anti-MDA5 + DM patients had RPILD at the time of serum sample collection (39.0%). Serum YKL-40 levels were significantly higher in anti-MDA5 + DM patients with RPILD compared with those without (p = 0.011). One month after treatment, patients with aggravated ILD had increased YKL-40 levels, while those with stable/improved ILD had decreased YKL-40 levels. Higher serum levels of ferritin and YKL-40, as well as lower peripheral CD3 + T cell counts, were independently associated with poorer prognosis. Kaplan-Meier survival curve showed that the 6 months survival rate in patients with high serum YKL-40 level (> 80 ng/ml) was significantly lower than that in patients with low YKL-40 level (≤ 80 ng/ml) (67% vs 89%, p < 0.01).

Conclusion: YKL-40 can be useful as an indicator for the occurrence of RPILD and correlates with severity of ILD and poor prognosis in anti-MDA5 + DM patients. Closely monitoring and intensive treatment are suggested in anti-MDA5 + DM patients showing high level of YKL-40, especially levels > 80 ng/ml.