Background/Purpose: Interstitial lung disease (ILD) encompasses a group of disorders that are classified together based on similar clinical, radiographic and pathologic findings. ILD is highly associated with autoimmune connective tissue diseases (CTD), and the diagnosis of ILD necessitates investigation into the possibility of an occult CTD. In a substantial number of cases, this investigation reveals evidence of autoimmunity, serologically, clinically or in both domains, without fulfilling criteria of a specific CTD. This disease category has been termed interstitial pneumonia with autoimmune features (IPAF). The goal of this study was to describe the characteristics of a cohort of ILD patients that fulfil the IPAF criteria.

Methods: The study patients were identified from a Mount Sinai Hospital-Department of Pulmonary Medicine registry of patients with ILD. All of the patients were diagnosed with ILD based on either a high resolution CT (HRCT) of the chest or a lung biopsy. The electronic medical records were reviewed to determine if they fulfilled clinical and/or laboratory IPAF criteria. The radiology report from each patient’s HRCT was reviewed as well as pathology reports from lung biopsies when available. Patients were excluded if they fulfilled classification criteria for a specific autoimmune CTD, or if there was insufficient data to evaluate their case in each of the three domains in which IPAF is assessed (clinical, serologic, morphologic).

Results: Of 429 patients in the ILD registry, 32 met criteria for IPAF. Nineteen were female (59%) and 13 were male (41%). Twenty-nine out of 31 patients (91%), met serologic criteria for IPAF, with the most common being an ANA >1:320 in a diffuse, speckled or homogeneous pattern (16/32). The next most common serologic criterion was anti-CCP positivity (6/32). Other serologic criteria that were present in the study cohort included anti-Ro positivity (4/32), anti-RNP (3/32), ANA< 1:320 in a nucleolar pattern (2/32) and anti-tRNA synthetase (1/32). Fifteen of the 32 patients (47%) met clinical criteria for IPAF. Presence of Raynaud’s phenomenon was the most common (11/32) followed by inflammatory arthritis (5/32), digital edema (2/32) and palmar telangiectasia (2/32). Twenty-eight of the 32 patients (88%) met morphologic criteria for IPAF. Non spesific interstitial pneumonia (NSIP) on HRCT or on biopsy was the most common morphologic criterion (20/32). Other morphologic criteria included unexplained: pleural thickening (3/32), intrinsic airway disease (2/32), pulmonary vasculopathy (1/32), diffuse lymphoplasmacytic infiltrates on lung biopsy (1/32), and pericardial effusion or thickening (1/32).

Conclusion: In a single center, retrospective cohort of patients who meet the IPAF criteria, the great majority of patients have serologic and morphologic findings that support the diagnosis (91% and 88%, respectively). However, less than half of the patients in this cohort (47%), demonstrated clinical features of a systemic autoimmune disease. Identifying patients with IPAF early during the disease course may be important since there is evidence of a favorable response to immunosuppressive therapy.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/clinical-serologic-and-morphologic-features-of-interstitial-pneumonia-with-autoimmune-features-ipaf-a-single-center-experience/