The goal of this observational study is to learn about risk of progressive pulmonary fibrosis (PPF). The main questions it aims to answer are: * Risk factors of PPF * Prevalence of PPF * Mortality of PPF Patients with interstitial lung disease (ILD) of known or unknown etiology other than IPF who has radiological evidence of pulmonary fibrosis will enroll in this study. * All participants will have baseline investigations at the first visit having provided informed consent. * At the first visit, baseline characteristics will be collected including demographics, medical history, smoking history, complications and medication use. 50 mL of blood will be obtained. High resolution computed tomography (HRCT), full lung function tests and a 6 min walk test will be performed. * Further visits at 6 months and 12 months will include further 50 mL blood sampling. HRCT, full lung function tests and a 6 min walk test will be repeated.