Isolated extranodal sinus histiocytosis presenting as an intramedullary spinal cord tumor with paraplegia. Case report.

Sinus histiocytosis with massive lymphadenopathy (Rosai-Dorfman disease) is a nonneoplastic lymphoproliferative disorder that usually presents with massive painless cervical lymphadenopathy accompanied by fever and weight loss. Extranodal involvement occurs in over 40% of patients; however, isolated extranodal disease without lymph node involvement is unusual. Extranodal involvement of the nervous system is unusual and isolated central nervous system disease in the absence of nodal disease is distinctly rare. The author describes the case of a 35-year-old man who presented with paraplegia and an enhancing intramedullary lesion on magnetic resonance imaging that was suggestive of a primary spinal cord tumor. The lesion was completely resected and histologically proved to be consistent with an isolated extranodal case of Rosai-Dorfman disease. Although a number of cases of this entity involving the CNS have been published, the author believes this case represents the first report of intramedullary spinal cord involvement as the initial and only sign of disease.