Arginine Vasopressin Deficiency Heralding Rosai-Dorfman Disease With Neurological Manifestations.

Rosai-Dorfman disease (RDD) is a rare heterogeneous disorder of non-Langerhans cell histiocytosis. The patient is a 24-year-old woman who presented with a 1-month history of polydipsia, polyuria, and 25-lb (11.3-kg) weight loss over 6 months and was found to have significantly elevated 24-hour urine volume (8.4 L). Prior to completion of the work-up for her presenting symptoms, she returned with a new complaint of disabling back pain and bilateral lower-extremity numbness with weakness refractory to conservative treatment. Magnetic resonance imaging (MRI) showed a prominent T2 to T4 stenosis from a soft tissue mass. Due to progressive pain and accelerating neurological symptoms, she was admitted for surgical debulking and biopsy. In the 10 hours she was unable to drink fluids surrounding her procedure, her serum sodium climbed to 160 mmol/L (reference interval, 137-145 mEq/L; [137-145 mmol/L]). Urine testing and desmopressin challenge revealed arginine vasopressin deficiency (AVP-D), formerly known as central diabetes insipidus. Pituitary MRI showed a mildly enlarged pituitary gland with loss of normal posterior pituitary signal supporting the diagnosis. Epidural mass pathology showed predominant histiocytes indicating RDD. This case highlights the diverse clinical manifestations of RDD and is an unusual instance of RDD linked with AVP-D and neurological involvement.