Therefore, with these assumptions in mind, in our study, we first analyzed the expression profile of KL-6 in bronchoalveolar lavage (BAL) and in the serum of patients with progressive pulmonary fibrosis (PPF) and non-progressive pulmonary fibrosis (nPPF) to specify both local and systemic behavior of fibrosis and to assess any differences in expression of this glycoprotein between progressive versus non-progressive forms of fibrosis. The gene discussed is MUC1; the disease is fibrosis.