“…Clinicians should be aware that eventually, a majority of patients with fibrotic ILDs will experience disease progression, sometimes several years after the diagnosis; therefore, long-term follow-up is warranted. Compared with those with connective tissue disease-associated ILD, patients with fibrotic hypersensitivity pneumonitis and those with non-IPF idiopathic interstitial pneumonia more frequently experienced disease progression and had a greater risk of death after satisfying PPF criteria, paralleling previous studies (13)(14)(15)(16). Thus, heterogeneity in disease course remains among ILD subtypes even after satisfying PPF criteria.…”