Involvement of the axial skeleton in sarcoidosis is a rare condition. Herein we report a case with an extensive axial sarcoidosis whose plain radiographs were non-informative. The present case suggested that osseous lesions on sacrum and iliac bones might cause misdiagnosis of sacroiliitis in plain radiographs and advanced imaging may be necessary to make an accurate diagnosis. Our case also underscores the importance of magnetic resonance imaging in selection of a suitable biopsy site to establish diagnosis.