In contrast, circulating KL-6 levels were shown to be markedly increased in particular types of drug-induced lung injury such as diffuse alveolar damage and chronic interstitial pneumonia patterns [15], and an elevated serum KL-6 level is one characteristic of active HP (1,508 ± 647 U/ml [5]). Here, MUC1 is linked to hypersensitivity pneumonitis.