['The different characteristics of usual interstitial pneumonia in patients with primary Sjögren׳s syndrome (UIP/pSS) compared with idiopathic pulmonary fibrosis (UIP/IPF) are not fully understood. This study aimed to compare characteristics, prognosis, and treatment responses in these patients.', 'Among 129 consecutive patients who underwent surgical lung biopsy to diagnose diffuse lung diseases at Kanagawa Cardiovascular and Respiratory Center between 1998 and 2002, we identified 10 and 19 patients with UIP/pSS and UIP/IPF, respectively. Baseline characteristics, chest high-resolution computed tomography (HRCT) and pathological findings, and the clinical course were compared between the two groups. Responses to immunosuppressive therapy were analyzed by comparing pulmonary function and clinical status before and one year after treatment initiation.', 'More patients in the UIP/pSS group tended to be female and older than those in the UIP/IPF group (mean age, 68 years vs. 62 years). In addition, they more commonly exhibited enlarged mediastinal lymph nodes and bronchial wall thickening on HRCT. Pathologically, in the UIP/pSS group, interstitial inflammation, plasma cell infiltration, lymphoid follicles with germinal centers, cysts, bronchiolitis, and pleuritis were significantly more prominent, whereas smooth muscle hyperplasia and fibroblastic foci were milder (all P<0.05). The prognosis was better for UIP/pSS compared with UIP/IPF patients (P=0.01). In addition, immunosuppressive therapy provided better disease control for those with UIP/pSS (83%, 5/6) compared UIP/IPF (7%, 1/15).'] Does features of usual interstitial pneumonia in patients with primary Sjögren׳s syndrome compare with idiopathic pulmonary fibrosis?