Background/Purpose: Connective tissue diseases (CTDs) are systemic autoimmune disorders that can compromise the lung. Interstitial lung disease (ILD) is one of the mayor forms of lung involvement in CTDs. Main CTDs with lung involvement are Rheumatoid Arthritis (RA), Systemic Sclerosis (SSc) and Idiopathic Inflammatory Myopathies (IIM) spectrum. ILD can be the first or the only manifestation of a CTD. Some ILD patients who don´t meet specific CTD classification criteria but have autoinmune findings have been classified as interstitial pneumonias with autoinmune features (IPAF). CTD related ILD (CTD-ILD) have the same patterns than idiopathic ILD, with predominace of non-specific interstitial pneumonia (NSIP). Response to immunosuppressive (IS) therapy and prognosis of CTD-ILD can be better than idiopathic ILD and it may be necessary to treat extra-thoracic disease, so oportune diagnosis of an underlying CTD is essential. The aim of this study is to describe the clinical and radiological features of a historical cohort of patients with CTD-ILD in a specialized pneumo-rheumatology clinic.

Methods: The study was conducted at the Instituto Nacional del Tórax in Santiago, Chile, a national referral center for ILD. It is a retrospective study of a historical cohort started in 2012 by the authors. All patients were evaluated in a multidisciplinary team. Descriptive statistics were done. For comparison alfa 0,05 two tails was used; for multiple comparisons Bonferroni correction was used. Analysis was done in Stata 14.0

Results: 219 patients were included in the study. Their main clinical and radiological characteristics are summarized on Table 1.  All patients are hispanic, with female predominance (84,5%). Main CTDs were RA, SSc and IIM. 15 patients (6,8%) met IPAF criteria. NSIP was the overall predominant ILD pattern (Table 1, Graphic 1).  In 34,7 % of patients diagnosis of ILD was done before CTD, in 27,4 % diagnosis of CTD/ILD was concomitant and in 38 % ILD was diagnosed after CTD. Mean FVC and DLCO at ILD diagnosis were 75% and 47,7% respectively.  49 patients (22%) didn´t get IS therapy due to mild and stable lung disease. 20 patients (9,1%) died in the period of observation. Main first line IS were Azathioprine, Mycophenolate or Cyclophosphamide.

Conclusion:  Our cohort show the same kind of CTDs with lung involvement and related ILD patterns described in other series and worldwide literature.  There might be an increase in ILD patients meeting IPAF criteria in the future.