Background/Purpose: A particular subset of interstitial pneumonia, associated to one or more clinical and serological features, suggesting a possible underlying autoimmune disorder, has been described and recently named Interstitial Pneumonia with Autoimmune Features (IPAF). Its prevalence and prognosis remains controversial and seems to include a very heterogeneous population. Our objective was to evaluate patients with interstitial lung involvement seen at a university hospital in Latin America in order to determine IPAF frequency and characteristics.

Methods: All electronic medical records of patients seen by pneumonologists during a 1 year at our hospital because of an interstitial lung disease (ILD) were reviewed by a rheumatologist and a pneumonologist in conjunction. Patients were classified in 3 groups: Idiopathic Pulmonary Fibrosis (IPF), IPAF and Interstitial Pneumonia associated with a connective tissue disease (IP-CTD). Demographic and clinical data, images features, lung function tests, and survival were recorded. Patients’ characteristics were compared between groups and a multivariate logistic regression analysis was performed in order to identify associations with an autoimmune ILD.

Results: 80 patients were seen in 1 year with ILD: 31 with IFP (38.8%), 3 with IPAF (3.8%) and 46 (57.5%) with IP-CTD. Patients’ characteristics are shown in table 1. Rheumatologic diseases with IP-CTD were Lupus in 2 patients, Mixed Connective Tissue Disease in 6, Limited Systemic Sclerosis in 2, Diffuse Systemic Sclerosis in 19 and 1 Inflammatory Myopathy. During a median follow up of 4.8 years (IQR 3.8-6.9) after ILD diagnosis, 5 patients died (6.3%): 3 with IFP and 2 with IP-CTD. Gender, Age and Physiology score (GAP) was associated with mortality as it has been previously described (OR 1.76, 1.02-3.07). In patients with IFP, CT pattern was UIP in 41.9% (CI 25.7-60.1%) and NSIP in 35.5 % (CI 20.5-54.0%). On the other hand, patients with IP-CTD, NSIP was the most frequent pattern in 60.0% (CI 44.8-73.5%), and 24.4% (13.9-39.4%) had an UIP pattern. Although NSIP was more frequent in autoimmune related ILD, it was not independently associated to it. In the multivariable logistic regression analysis female sex (OR 10.5, CI 2.75-40.15) and a younger age (OR 0.94, CI 0.89-0.98) were associated with an autoimmune ILD diagnosis.

Conclusion: when evaluated together by a rheumatologist and a pneumonologist, IPAF diagnosis was very rare (3.8%). An autoimmune ILD disease must be suspected in females and younger patients.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/interstitial-pneumonia-with-autoimmune-features-is-it-frequent/