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. Subsequent CT of the chest showed micronodular thickening of fissures, subpleural micronoduli and multiple enlarged hilar and mediastinal lymph nodes, in keeping with pulmonary sarcoidosis (not shown). On [F]Fluorodeoxyglucose positron emission tomography (FDG-PET)-CT, multiple foci of increased FDG uptake in the pelvis, spine and mediastinum were seen (Fig. C, arrows). Transbronchial needle aspiration of the PET-positive infracarinal lymph nodes confirmed the presence of non-caseating granulomas. The patient’s symptoms resolved spontaneously.