Clinical significance of histological inflammation in systemic sclerosis-associated interstitial lung disease

Background: Systemic sclerosis-associated interstitial lung disease (SSc-ILD) is known to have a poor prognosis and the relationships between histological findings and response to anti-inflammatory therapy or prognosis have not been well investigated.<br /> Methods: We examined SSc-ILD patients who underwent surgical lung biopsy at a single respiratory center between 2008 and 2021 and received anti-inflammatory therapy (corticosteroids and/or immunosuppressive drugs). These patients were classified into two groups: an inflammation group, where histological evidence of inflammation defined as "lymphoid aggregates with germinal centers" or "plasmacytosis" was observed, and a non-inflammation group, where these findings were not observed. The correlation of the histological conclusions of inflammation with treatment response and prognosis was retrospectively investigated.<br /> Results: Twenty-seven patients were included in the study; 15 (55.6%) were allocated to the inflammation group and 12 (44.4%) to the non-inflammation group. Patient backgrounds did not differ between the groups. The first annual increase in % predicted FVC was significantly larger in the inflammation group than in the noninflammation one (from 74.3% to 85.9% vs. 75.0%-74.7%, respectively; p = 0.021). The inflammation group took significantly longer to reach end-stage lung disease, defined as an FVC <50%, needing continuous oxygen, or death (p = 0.011). They also had a trend towards longer overall survival compared to the non-inflammation group (median survival: not reached vs. 6.6 years, p = 0.083). Conclusions: Approximately half of the SSc-ILD patients showed histological evidence of inflammation, which may influence treatment response and long-term disease progression.