Background Lung imaging findings vary among subtypes of connective tissue disease-associated interstitial lung disease (CTD-ILD), leading to both diagnostic and therapeutic challenges.

Objectives We performed a comprehensive assessment of ILD morphology across CTD-ILD subtypes by examining the presence of overall imaging patterns and specific morphological features.

Methods High-resolution chest computed tomography (HRCT) of patients with CTD-ILD enrolled in the multicentre Canadian Registry for Pulmonary Fibrosis from their first ILD clinic visit were re-reviewed in standardized multidisciplinary discussion. All CTD diagnoses were rheumatologist-confirmed. An experienced chest radiologist blinded to clinical data quantified the percentage of lung parenchyma affected by honeycombing, reticulation, ground glass opacity (GGO), hypoattenuating lobules, consolidation, and emphysema. Gas trapping was evaluated on expiratory CT. Each case was categorized into an overall disease pattern including usual interstitial pneumonia (UIP), non-specific interstitial pneumonia (NSIP), fibrotic hypersensitivity pneumonitis (fHP), lymphocytic interstitial pneumonia (LIP), and unclassifiable.

Results 615 patients with CTD-ILD were assessed with 215 (33%) having systemic sclerosis (SSc), 127 (20%) rheumatoid arthritis (RA), 100 (16%) idiopathic inflammatory myopathy (IIM), 61 (9%) mixed connective tissue disease (MCTD), 40 (6%) Sjogren’s syndrome (SS), 19 (3%) lupus (SLE), and 83 (13%) undifferentiated connective tissue disease (UCTD). NISP was most predominant in SSc (76%), IIM (62%), and MCTD (66%), while UIP was most common in RA (47%) and SS (33%). A fHP pattern was most common in RA (15%), SLE (21%), and MCTD (12%) (Figure 1a). There was substantial variability in the extent of fibrotic (honeycombing, reticulations) and non-fibrotic (pure GGO, consolidation) parenchymal features within and across each CTD (Figure 1b).

Conclusion There is considerable variation in imaging features across subtypes of CTD-ILD, with NSIP generally most common, UIP most frequent in RA and SS, and fHP less frequent but most common in RA, SLE, and MCTD. This variability highlights the need for additional data on management of CTD-ILD that considers the potential for variable treatment responses across major CTD-ILD subtypes and phenotypes.

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REFERENCES: NIL.

Acknowledgements: NIL.

Disclosure of Interests Boyang Zheng: None declared, Daniel-Costin Marinescu: None declared, cameron hague: None declared, Nestor Muller: None declared, darra murphy: None declared, Andrew Churg: None declared, Joanne Wright: None declared, Amna Al-Arnawoot: None declared, Gerald Cox: None declared, Zachary Guenther: None declared, Amanda Grant-Orser: None declared, James Huynh: None declared, Tracy Elliot: None declared, Derek Fladeland: None declared, Jen Ellis: None declared, geoff karjala: None declared, Gillian Goobie Grant/research support from: Boehringer Ingelheim.

Pulmonary Fibrosis Foundation, Kerri Johannson Paid instructor for: Boehringer-Ingelheim, Hoffman-La Roche Ltd, Consultant of: Boehringer-Ingelheim, Hoffman-La Roche Ltd, Pliant Therapeutics, Stacey Lok Speakers bureau: Boehringer Ingelheim, Tony Sedlic: None declared, Nasreen Khalil: None declared, Veronica Marcoux Grant/research support from: Astra Zeneca, Roche, Boehringer Ingelheim, Martin Kolb Speakers bureau: Roche, Novartis, Boehringer Ingelheim, Grant/research support from: Boehringer Ingelheim, Pieris, Roche, Ciaran Scallan: None declared, Nathan Hambly Speakers bureau: Boehringer Ingelheim, Janssen, Roche, Grant/research support from: Boehringer Ingelheim, Janssen, Roche, sarah macisaac: None declared, Jonathon Leipsic Speakers bureau: GE Healthcare, Philips Healthcare, victoria tan: None declared, celine durand: None declared, Helene Manganas Grant/research support from: Boehringer Ingelheim Canada, Hoffmann La Roche, Galapagos, BMS, Ehsan Haider Speakers bureau: Boerhinger Ingelheim, Jolene Fisher Speakers bureau: Boehringer-Ingelheim, Consultant of: Boehringer-Ingelheim, AstraZeneca, micheal mcinnis: None declared, shane shapera Consultant of: AstraZeneca, Boehringer Ingelheim, Hoffman LaRoche, Ana-Maria Bilawich: None declared, John Mayo: None declared, patrick bourgouin: None declared, julie morisset Speakers bureau: Roche, Boehringer Ingelheim, Kelly Sun: None declared, Alyson Wong: None declared, Christopher Ryerson Speakers bureau: Boehringer Ingelheim, Hoffmann-La Roche, Astra Zeneca, Consultant of: Boehringer Ingelheim, Hoffmann-La Roche, Astra Zeneca.