A rare case of extra nodal Rosai-Dorfman disease with isolated multifocal osseous manifestation.

Sinus histiocytosis with massive lymphadenopathy (SHML) or Rosai-Dorfman disease is a non-neoplastic condition which typically presents as massive, bilateral cervical lymphadenopathy and can involve multiple extranodal organ systems such as skin, eyes, and upper respiratory tract in about 28% cases. Bone lesions in association with nodal disease are seen in less than 10% cases. Isolated bone involvement as the only manifestation of SHML is extremely rare, with less than 50 cases reported in the literature. We report a very uncommon case of Rosai-Dorfman disease with isolated multifocal osseous involvement as the only presenting feature, involving about 10 different sites with no lymphadenopathy or other organ system involvement.