Isolated Osseous Rosai Dorfman Disease of Foot Bones. Report of a Patient Misdiagnosed and Treated as Chronic Osteomyelitis.

Isolated osseous involvement without lymphadenopathy is a rare manifestation of Rosai-Dorfman disease. It clinically and radiologically mimics infections and primary bone tumors. The present report describes a 9-year-old girl with multifocal monomelic osseous involvement as an isolated manifestation. She presented with lytic lesions in the left proximal phalanx of the great toe and head of the second metatarsal unaccompanied by disease elsewhere. She was treated outside as chronic osteomyelitis. After 9 months, the swelling recurred, and a repeat biopsy was suggestive of Rosai-Dorfman disease. This report highlights the diagnostic challenges in patients with extra nodal isolated bone involvement, especially on small biopsies.