Extranodal Rosai-Dorfman disease with multifocal bone and epidural involvement causing recurrent spinal cord compression

Sinus histocytosis with massive lymphadenopathy, or Rosai-Dorfman disease, is a rare histiocytic disorder that typically presents with chronic, self-limiting, cervical lymphadenopathy. We present a case, a diagnostic dilemma for multiple consultation services, of an otherwise well 17-year-old boy without lymphadenopathy who, 8 months after excision of a T9 lytic vertebral lesion and epidural mass that caused cord compression, again presented with cord compression from progressive vertebral disease, recurrent epidural mass, and development of a paraspinal mass and tibial lesion. The excised vertebral and epidural lesions, 2 paraspinal biopsies, and tibial biopsy were interpreted as chronic inflammation until large histiocytes were noted, which were positive for CD68, S100 protein, fascin, and MAC387, and demonstrated characteristic emperipolesis (lymphophagocytosis) that was diagnostic of Rosai-Dorfman disease. This atypical clinical behavior and sites of involvement of multiple bones but not of lymph nodes is unusual and constitutes the aggressive end of the clinical spectrum and a rare cause for cord compression.