OBJECTIVES: Axial bone involvement in sarcoidosis is observed in approximately 25 % of patients on positron emission tomography (PET). Many of these lesions are asymptomatic, and their long-term outcomes are not well defined. This study aims to evaluate the prognosis of axial bone lesions in histologically confirmed sarcoidosis. METHODS: We assessed initial and follow-up MRI and PET from 48 patients diagnosed with axial bone sarcoidosis (135 MRI and 132 PET), with a mean follow-up duration of 33 and 44 months, respectively. Baseline and longitudinal associations between imaging results and patient variables were evaluated. RESULTS: MRI revealed predominantly nodular marrow replacement lesions, while PET identified multifocal bone involvement, with no corresponding bone lesions detected on CT in 80.8 % of cases. Compared to baseline imaging, serial MRI and PET showed significant reduction or resolution of bone lesions over time (MRI: p <
0.01
PET: p <
0.001). This was more frequently observed on PET (68.3 % of patients) than on MRI (19.5). During follow-up, bone pain improved significantly (p = 0.01), which was associated with favorable changes in both PET and MRI findings (p = 0.02 and p = 0.04, respectively). Seven patients had bone relapse. No epiduritis or soft-tissue infiltration was observed. DISCUSSION: This longitudinal evaluation over a 3-year period, combining clinical, radiological, and biochemical data, shows that sarcoidosis axial bone lesions have a favorable prognosis. Significant improvement was observed on both MRI and PET. The improvement in bone pain was associated with favorable imaging changes.