Additionally, patients with serum KL‐6 levels greater than 1000 U/ml had significantly worse lung function values in forced vital capacity (FVC) %pred, forced expiratory volume in 1 s (FEV1) %pred, and total lung capacity (TLC) %pred and higher radiological fibrosis scores compared with the group with serum KL‐6 < 500 U/ml. This evidence concerns the gene MUC1 and fibrosis.