Abstract Rationale Fibrosing interstitial lung diseases (f-ILD) often present with nonspecific radiographic findings, but certain CT patterns are more specific to autoimmune diseases (AID) and can help narrow diagnosis. Our aim was to identify distinctive fibrosis patterns and signs associated with AID on computed tomography (CT) in patients with idiopathic pulmonary fibrosis (IPF), interstitial pneumonia with autoimmune features (IPAF), and AID-associated interstitial lung disease (AID-ILD). Methods A retrospective analysis was conducted to identify CT reports of patients with f-ILD presented at the multidisciplinary committee between 2018 and 2024. Radiologists assessed recently described CT signs of variant fibrosis patterns in autoimmune disease (AID). Results 22 patients with variant fibrosis patterns were identified (median age: 68 years; 13 men). Patterns included exuberant honeycombing (50%), island-like (27.27%), straight-edge (18.18%), and four-corner sign (4.54%) signs. The most common pattern was exuberant honeycombing, observed in 100% of IPF patients (n = 3), and correlated with the UIP pattern. IPAF patients (n = 6) exhibited various patterns, including straight-edge (50%), island-like (33.3%), and exuberant honeycombing (16.67%). In AID-ILD patients (n = 13), exuberant honeycombing (53.84%) and island-like (30.76%) were the most frequently observed patterns. Conclusions CT signs of variant fibrosis patterns suggestive of AID can also be found in idiopathic ILDs, such as IPF, as well as in IPAF patients. Their significance remains unknown, but identifying these signs may facilitate earlier AID-ILD diagnosis and support comprehensive evaluation and follow-up. Including these distinctive fibrosis patterns associated with AID in the IPAF criteria might be useful. This abstract is funded by: Instituto de Salud Carlos III, FEDER Funds (FIS17/00369, 585 FIS19/01152, FIS23/00924), SEPAR, SOCAP.
Hernandez-Gonzalez et al. (Fri,) studied this question.