Cutaneous Rosai-Dorfman disease of the forearm: case report.

Sinus histiocytosis with massive lymphadenopathy, also known as Rosai-Dorfman disease (RDD), is a rare non-neoplastic pathologic condition that frequently pursues a prolonged clinical course marked by exacerbations and remissions. Cutaneous RDD is even less common than cases involving lymph nodes. We present the case of a patient with long-standing Crohn's disease who developed cutaneous RDD in the forearm.