AB0789 AXIAL BONE INVOLVEMENT IN SARCOIDOSIS HAS A GOOD PROGNOSIS: A COHORT STUDY OF 48 PATIENTS
Authors: S. Challal, R. Elodie, B. Lanseur, F. Jeny, H. Nunes, M. Soussan, M. C. Boissier, L. Semerano, N. Saidenberg Kermanac’h
Journal: Annals of the Rheumatic Diseases (2024)

<h3>Background:</h3> Axial bone involvement is a frequent finding in sarcoidosis. Around 25% of PET scans of patients with sarcoidosis show focal or diffuse bone FDG uptake, most often in the spine (47%) and pelvis (40%) [1]. The evolution of these lesions has never been systematically studied, which constitutes a diagnostic, prognostic, and therapeutic challenge. <h3>Objectives:</h3> To determine the prognosis of axial bone lesions in sarcoidosis and to study their association with clinical and biological variables in a cohort of sarcoidosis patients. <h3>Methods:</h3> We included patients from the rheumatology department of Avicenne teaching hospital (Bobigny, France), with histologically proven sarcoidosis, with PET or MRI (spine/pelvis) showing focal or diffuse bone abnormalities. The follow-up of baseline imaging abnormalities (MRI1/PET1) was carried out in the context of patients' care. All the images were independently analyzed by two readers. <h3>Results:</h3> 48 patients (32 women and 16 men) were included: median age at sarcoidosis diagnosis was 49.5 years (RANGE 28- 72); mean age at bone involvement diagnosis was 53.5 years (RANGE 28-75). Multivisceral involvement (most often splenic, hepatic and cutaneous) was present in 56.25% of patients. We reviewed 135 MRI and 132 PET scans, with a mean follow-up of 33 and 44 months respectively between the first and the last scan. All available MRI1 (n=42) showed abnormalities: 30 nodular or micronodular lesions with low T1/high T2 signal and contrast enhancement, 7 patchy lesions and 5 showed both. The great majority (40/47) of PET1 scans showed multiple focal bone FDG uptake, 2 showed diffuse bone uptake, and 5 showed no uptake. Interestingly, only 9/47 PET1 scans showed bone lesions at CT-scans (5 condensing and 4 lytic), while 38/47 showed no abnormalities. Over the longest follow-up period (41 MRI and 41 PET scans), 10 MRI and 6 PET scans were stable, 20 MRI and 4 PET scans showed regression of the lesions, 6 MRI and 21 PET scans showed disappearance, and 5 MRI and 7 PET scans showed worsening lesions. In 7 patients bone lesions reappeared after regression or disappearance during follow-up. Among 65 PET scans and MRI performed at the same time (at baseline or follow-up), the concordance was: 43 PET+/MRI+, 3 PET-/MRI-, 0 PET+/MRI-, 19 PET-/MRI+. Among the 26 patients in whom bone lesions were painful at baseline 21 progressed favorably (10 improvements and 11 resolutions), and 5 remained stable. All 22 asymptomatic patients at baseline remained asymptomatic. In 32/48 patients treatment was indicated by bone involvement itself: 17 received hydroxychloroquine, 7 methotrexate, 3 both, 2 corticosteroids alone, 3 infliximab. No patient had neurologic compression complication during follow-up. Baseline CTX levels were high (median 735, range 148-2591UI), and lowered during follow-up (421, range 130-956). Baseline ACE was elevated in 22/44 patients vs. 9/42, during follow-up. Only 3 had hypercalcemia at baseline. Mean T-score was -0.8 DS at the lumbar spine and -0.6 DS at the total hip. A total of 9 patients had osteoporosis and 4 experienced during the follow-up an osteoporotic vertebral fracture. No clinical or biological variables were associated with baseline imaging data, or were predictive of bone lesion outcome. <h3>Conclusion:</h3> This is the first study to characterize the evolution of axial bone lesions in sarcoidosis. The prognosis was good, with a mostly favorable radiological and clinical course. PET FDG uptake may reflect more active lesions, while MRI abnormalities seem to persist longer. Bone involvement was asymptomatic in half of the cases. No clinical or biological variable was associated with bone involvement or predicted the evolution of bone lesion over time. <h3>REFERENCES:</h3> [1] Soussan M, Augier A, Brillet PY et al. Functional imaging in extrapulmonary sarcoidosis: FDG-PET/CT and MR features. <i>Clin Nucl Med</i>. 2014;39:e146-59. doi: 10.1097/RLU.0b013e318279f264. PMID: 23579973. <h3>Acknowledgements:</h3> <b>NIL.</b> <h3>Disclosure of Interests:</h3> <b>None declared.</b>