Rosai-Dorfman disease is a rare disorder characterized by overproduction (proliferation) and accumulation of a specific type of white blood cell (histiocyte) in the lymph nodes of the body (lymphadenopathy), most often those of the neck (cervical lymphadenopathy). In some cases, abnormal accumulation of histiocytes may occur in other areas of the body besides the lymph nodes (extranodal). These areas include the skin, central nervous system, kidney, and digestive tract. The symptoms and physical findings associated with Rosai-Dorfman disease vary depending upon the specific areas of the body that are affected. The disorder predominantly affects children, adolescents or young adults. The exact cause of Rosai-Dorfman disease is unknown.