MUC1 and interstitial lung disease: Patients with acute exacerbation of underlying ILD (AE-ILD; 963.6 U/mL) also had a higher median serum KL-6 level than those without ILD (p = 0.023) or those with RP (p = 0.028), although there was no significant difference compared to patients with DILD (Fig. 3b).