A Singular Case of Intracranial Sinus Histiocytosis without Massive Lymphadenopathy: Isolated Rosai-Dorfman Disease of the Hypothalamus.

BACKGROUND: Sinus histiocytosis with massive lymphadenopathy (also known as Rosai-Dorfman disease [RDD]) is a benign but chronic cervical lymphadenopathy associated with systemic inflammation. Although extranodal manifestations of RDD have been described, isolated central nervous system (CNS) involvement is exceedingly rare. CASE DESCRIPTION: We present the case of a 66-year-old woman who presented with 3 weeks of intermittent headaches, diplopia, and increasing confusion who was found on work-up to have isolated hypothalamic RDD, evidenced by a dense admixture of large histiocytic cells admixed with numerous small mature lymphocytes and some scattered plasma cells and neutrophils on stereotactic brain biopsy. Over 19 months of follow-up, neurologic examination continues to reveal stable bilateral partial abducens nerve palsies without diplopia, and a new gradual onset short-term memory loss. Interim treatment for the histiocytic lesion consisted of 10 cycles of external-beam radiation therapy along with high-dose steroids. The patient currently experiences minimal functional loss from treatment of her intracranial sinus histiocytosis, with a Karnofsky performance status of 80, and she remains without any disease involvement outside of the CNS. CONCLUSION: Because misdiagnosis of a hypothalamic contrast-enhancing lesion could potentially lead to therapeutic mismanagement and poor outcomes, it is important to consider RDD in the differential diagnosis.