Musculoskeletal sarcoidosis: spectrum of appearances at MR imaging

Magnetic resonance (MR) imaging reveals a broad range of musculoskeletal abnormalities in patients with sarcoidosis, including focal and diffuse muscle lesions, soft-tissue masses, joint abnormalities, and marrow infiltration of small and large bones. Long bone and axial skeletal involvement may be occult at conventional radiography but depicted at MR imaging, with an appearance that resembles that of osseous metastases. Sarcoidosis-related findings may be detected at dedicated MR imaging for osteoarticular symptoms in sarcoidosis patients or encountered incidentally at MR imaging performed for other indications. Correlation with clinical and laboratory findings is essential for correct diagnosis because the MR imaging findings are nonspecific in most cases. The radiologist should be aware of potential sarcoidal causes in the differential diagnosis of musculoskeletal lesions in patients with proved or suspected sarcoidosis. Such consideration will have a profound effect on the interpretation of images and on the study of patients with dual diagnoses of sarcoidosis and neoplasm.