A rare presentation of isolated intraosseous Rosai-Dorfman disease of the tibia – The role of whole-body magnetic resonance imaging in management

Rosai–Dorfman disease (RDD) is a rare non-Langerhans histiocytic disorder, usually presenting with enlarged cervical lymph nodes. Extranodal involvement is quite common and synchronously involves the nasal cavity, paranasal sinuses, skin, orbit, central nervous system, and rarely bones. Isolated bone involvement is rare and can present with local symptoms such as pain, swelling, restriction of activity, and occasionally pathological fracture. The most common sites of osseous RDD are the cranium, facial bones, and tibia, in decreasing order of frequency. Imaging findings of primary osseous RDD can be variable and there are no key features to diagnose this entity with certainty. Hence, the primary role of imaging is to plan the management and post-treatment follow-up. Here, we present a case of primary osseous RDD involving tibial diaphysis and emphasize the importance of whole-body magnetic resonance imaging in ruling out systemic involvement.