A case of multisystem Langerhans cell histiocytosis presenting as central diabetes insipidus.

Langerhans cell histiocytosis (LCH) is a rare malignancy most commonly characterized by histiocytic infiltration of bone. LCH lesions in the skull place the adjacent central nervous system (CNS) at risk for involvement, which can manifest as central diabetes insipidus (CDI) when there is infiltration of the hypothalamic-pituitary axis. We present a case of a 39-year-old female who presented with polyuria and polydipsia for 1 year and left-sided hearing loss, gait instability, and nystagmus for 5 days. She was found on laboratory evaluation to have CDI and underwent left cortical mastoidectomy for a destructive peripherally enhancing mastoid lesion seen on MRI brain. Pathology revealed CD1a and S100+ LCH and the patient was subsequently discharged to begin outpatient chemotherapy with vinblastine and prednisone. The patient's CDI was diagnostic of CNS involvement, making her LCH multisystem through the infiltration of both the skull and hypothalamic-pituitary structures. As CDI can be seen in up to 25% of single-system LDH, and up to 50% of multisystem cases, radiologic studies to evaluate for osteolytic skull lesions must be considered as part of the evaluation for LCH when CDI has been diagnosed.