BackgroundAt early stages, SSc lung involvement is characterised by Ground Glass Opacities (GGO) at High Resolution Computed Tomography (HRCT). However, HRCT scan is not able to provide functional information and to discriminate between an “active inflammatory” and an “established fibrotic” GGO. 18Fluoro-Deoxy-d-Glucose (18F-FDG) Positron Emission Tomography/Computed Tomography (PET/CT) is able to detect metabolic activity picking up inflammation and provides both morphologic and metabolic data.ObjectivesThe aim of this study was to evaluate, if 18F-FDG PET/CT scan may identify the inflammatory component of GGO in SSc interstitial lung disease.MethodsSeven patients with SSc (1 male and 6 females; mean age 59.56 y±9.15 SD; median disease duration 5 years,2–11 who underwent 18F-FDG PET/CT scan because of cancer screening, were retrospectively analysed. HRCT images analysis led to classification of pulmonary segments as “negative” (normal morphology) and ”positive” (GGO). Furthermore, the “Warrick score” was used as a staging tool for SSc-ILD. Mean Standardised Uptake Value (mSUV) of segmental parechima was normalised (nmSUV) by comparison with the values of selected control subjets.ResultsNo SSc patient was affected by cancer. Three patients had a Warrick Score >0, while 4 patients did not had any lung involvement (Warrick Score=0). The 3 patients with a Warrick Score >0 had also skin involvement with a median mRSS 6 (2–7) and pathological lung FDG uptake. In “positive” segments of SSc patients, nmSUV was significantly higher than in the lung segments of the control population (mean estimation 1.53; C.I. 1.42–1.65, p<0.0001). In “negative” segments of SSc patients, with a Warrick score >0, the nmSUV was significantly higher than in segments of the control population (mean estimation 1.29; C.I. 1.22–1.37, p<0.0001). Lung segments with GGO showed an nmSUV higher (21%) than “negative” segments (C.I. 0.13–0.28, p<0.0001) of patients with Warrick score >0. “Negative” lung segments of patients with Warrick Score >0 showed a 32% higher 18F-FDG uptake than “negative” lung segments of patients with Warrick Score=0. (C.I. 0.17–0.48, p<0.0001). (figure 1)Abstract THU0425 – Figure 1a) Differences in 18F-FDG uptake between “positive” segments of Warrick score >0 SSc patients, “negative” segments of Warrick score >0 SSc patients and “negative” segments of Warrick score=0 SSc patients vs attended normalised control value (=1); b) Differences in 18F-FDG uptake between “positive” lung segments of SSc patients with Warrick score>0 vs “negative” segments of the same patients; c) Differences in 18F-FDG uptake “negative” lung segments of patients with Warrick Score>0 vs “negative” lung segments of patients with Warrick Score=0ConclusionsMorphologically “positive” GGO segments show an increased 18F-FDG uptake suggesting the existence of a metabolically active (inflammatory) GGO. However, in patients with GGO, negative lung segments showed a higher nmSUV than negative lung segments in patients without GGO. This may suggest that PET/CT may disclose an underlying inflammatory process, which cannot yet be evidenced by HRCT. Further studies on a larger population are warranted to confirm these data and possibly provide a prognostic significance of PET/CT positivity in SSc patients.Disclosure of InterestNone declared