Abstract: We report a case of a 39-year-old male with sinus histiocytosis with massive lymphadenopathy (Rosai-Dorfman disease, RDD). He was treated with intravenous rituximab at a dose of 500 mg per administration, concurrently with methotrexate. Following the third rituximab infusion, the facial rash had mostly resolved, the truncal rash had improved compared to before, and the lymph nodes had reduced in size.

Key words: sinus histiocytosis with massive lymphadenopathy, Rosai-Dorfman disease, rituximab, methotrexate, biological agents