A serum KL-6 of ≥ 1000 U/mL was previously reported to be a predictor of poor prognosis in patients with idiopathic pulmonary fibrosis [37], and in SSc-ILD, the presence of elevated KL-6 values is also a poor prognostic factor [38]. This evidence concerns the gene MUC1 and idiopathic pulmonary fibrosis.