MUC1 and idiopathic interstitial pneumonia: Among 14 patients with rapidly progressive IPF (defined as deterioration of dyspnea within 2 months and the presence of ground glass opacity on HRCT), Yokoyama et al. found that, after corticosteroid pulse therapy, baseline KL-6 levels were significantly decreased at 1 or 3 weeks in survivors (− 18.9 ± 14.4%, P < 0.05 and − 32.7 ± 20.9%, P < 0.05, respectively), whereas KL-6 levels tended to increase at 3 weeks in non-survivors (+ 93.7 ± 103%; P < 0.05)24.