We recently demonstrated that the relative changes in KL-6 over 1 week in patients with acute exacerbation of interstitial lung disease (AE-ILD) were independently associated with in-hospital mortality and that a marked change in KL-6 level (≥ 10%) is useful for differentiating patients with poor prognosis [17]. The gene discussed is MUC1; the disease is interstitial lung disease.