Fibrotic Pulmonary Sarcoidosis with Honeycomb-like Changes Mimicking Idiopathic Pulmonary Fibrosis/Usual Interstitial Pneumonia (IPF/UIP) in the Lower Lobes: A Case Treated with Anti-fibrotic Therapy.

Established fibrosis in pulmonary sarcoidosis is typically not progressive. However, progressive fibrosis similar to interstitial pneumonia occasionally occurs. We herein report a 49-year-old woman who was histologically diagnosed with sarcoidosis. She also had honeycomb-like manifestations in the lower lobes that resembled idiopathic pulmonary fibrosis on computed tomography, whereas pathological findings of a surgical lung biopsy suggested interstitial lung disease associated with rheumatoid arthritis. However, the patient did not develop clinical rheumatoid arthritis even after 17 years of follow-up. Notably, she showed progressive fibrosis and was treated with anti-fibrotic therapy. It is thus important to recognize progressive fibrosis in pulmonary sarcoidosis, although it is rare.