More than 70% of patients with different ILDs (idiopathic interstitial fibrosis, collagenosis, hypersensitivity pneumonitis, radiation pneumonitis, drug-induced pneumonitis, acute respiratory distress syndrome, sarcoidosis, alveolar proteinosis) had KL-6 serum levels exceeding 500 U/mL (26) and therefore, KL-6 cannot be considered a specific marker of silicosis. This evidence concerns the gene MUC1 and hypersensitivity pneumonitis.