Risk of progression of idiopathic pulmonary fibrosis to connective tissue disease: a long-term observational study in 527 patients.

Progression to CTD is uncommon in IPF patients. However, a significant number of IPF patients with high titers of RF, ACPA, or MPO-ANCA progressed to CTD. RF, ACPA, and MPO-ANCA might be significantly associated with CTD development in IPF patients. Key Points • A significant number of IPF patients with high titers of RF, ACPA, or MPO-ANCA progressed to CTD. • IPF/UIP with high titers of RF, ACPA, or MPO-ANCA might be the initial clinical manifestation of CTD. • RF, ACPA, and MPO-ANCA may be significantly associated with the development of pulmonary fibrosis in patients with CTD.