Bone marrow involvement in sarcoidosis

A 36-year-old woman presented with joint pain and swelling, not improving with nonsteroidal anti-inflammatory drugs. Plain radiographs of feet, ankles, pelvis and lumbar spine were unremarkable. To rule out seronegative spondylarthropathy, MRI of the sacro-iliac joints (SIJ) was performed. The SIJ were normal, but multiple, nodular zones of bone marrow replacement were seen within the iliac and ischial bones, sacrum and lumbar spine. The lesions were hypointense on T1-Weighted Images (WI) (Fig. A, arrows) and of intermediate to high signal intensity on T2-WI (Fig. B, arrows). Given the young age of the patient and relative minor complaints, sarcoidosis was suspected. Other differential diagnoses included metastatic disease, lymphoma, mastocytosis and widespread granulomatous infectious disease.