Background:Diffuse interstitial lung disease (ILD) is frequently associated with connective tissue diseases (CTD) and is one of the main causes of morbidity and mortality in these patients. Recently, the concept of Interstitial Pneumonia with Autoimmune Features (IPAF) has been defined to characterize ILD associated with systemic manifestations limited to subtle serological and clinical autoimmune abnormalities and not fulfilling the international criteria for the diagnosis of a given CTD.Objectives:The objective of this study is to describe the clinical, serological and radiological characteristics, as well as the treatment patterns of patients with ILD referred to a Rheumatology Service for suspected CTDMethods:Observational, cross-sectional study of 43 patients with ILD referred for evaluation to the medical consultation of CTD of the Rheumatology service at the Reina Sofía Hospital. Patients were classified as patients with defined CTD, patient with IPAF and patients with other types of pneumopathy. We conducted a descriptive study of all patients and compared the clinical-analytical-radiological characteristics and treatment patterns of the first two groups.Results:Of the 43 patients, 67.40% were women with a mean age at diagnosis of 65.65 (10.42) years and 53.50% of smoking patientsOf the total of patients, 16 (37.2%) were included in the CTD group, 17 (39.5%) met criteria for IPAF and 10 (23.3%) had another type of pneumopathy.In the CTD group scleroderma was the most frequent disease (6/16), followed by inflammatory myopathy (4/16), Sjögren’s syndrome (3/16), rheumatoid arthritis (2/16) and polymyalgia rheumatic (1/16). In this group of patients, the most common symptom was Raynaud’s phenomenon (RP) (7/16), followed by arthritis (7/16) and mechanic’s hands (3/16). Regarding the most frequently antibodies were ANA (100%), anti-RO (41.7%), anti-citrullinated protein antibodies (30%) and rheumatoid factor (RF) (28.6%).In patients with IPAF, as in the CTD group, the most observed clinical criterion was RP (5/17), followed by arthritis (1/17) and mechanic’s hands (1/17). Among the serological criteria the most common antibodies were ANA (100%), followed by anti-RO (33.3%), anti-RNA synthetase (28.6%) and RF (22.2%).Regarding the radiological pattern, in both groups the most frequent was nonspecific interstitial pneumonia, followed by the indeterminate pattern and usual interstitial pneumonia (UIP) in third place. There were no significant differences by gender and age, between the group of CTD and IPAF, observing in both groups a predominance of women with a similar mean age, being the upper smoking habit in the IPAF group (70.6% vs 31.5%, p= 0.02). Regarding the treatment used, the use of immunosuppressants (IS) was more frequent in CTD group (56.3% vs 11.8%, p = 0.007).Conclusion:The clinical-serological and radiological characteristics were similar among patients with IPAF and CTD, which supports the notion of a similar pathophysiology in both groups. In our cohort patients with CTD received IS more frequently than IPAF group, however, future work would be necessary to assess whether the response to treatment is similar in these populations and if IS can benefit patients with IPAF to long term. In addition, it could be useful to include the UIP pattern within the IPAF classification criteria, not currently included, since it is the third most frequent radiological pattern.References:[1]Respirology, 21 (2016), pp. 245-258[2]Eur Respir J, 46 (2015), pp. 976-987Disclosure of Interests:Rafaela Ortega Castro: None declared, Pérez Sánchez Laura: None declared, Font Ugalde Pilar: None declared, Jerusalem Calvo Gutierrez: None declared, Antonio Requejo-Jimenez: None declared, Simona Espejo-Pérez: None declared, Teresa Gonzalez-Serrano: None declared, María del Carmen Castro Villegas: None declared, Gómez García Ignacio: None declared, Alejandro Escudero Contreras: None declared, Eduardo Collantes Estevez Grant/research support from: ROCHE and Pfizer, Speakers bureau: ROCHE, Lilly, Bristol and Celgene, Maria A Aguirre: None declared