7418 Xanthoma Disseminatum - A Rare cause of Diabetes Insipidus

Abstract Disclosure: P. Balasubramanian: None. J. Cohen: None. Z. Corbin: None. G. Panse: None. S.E. Inzucchi: None. Background: Xanthoma disseminatum is a rare non-Langerhans cell-derived benign histiocytosis of unknown etiology, characterized by mucocutaneous xanthomatosis. Systemic involvement occurs in a subset of patients, the most common manifestation being central diabetes insipidus in the setting of hypothalamic-pituitary- infundibulum infiltration, occurring in about 30-50% of the patients. We present the case of a man with biopsy proven cutaneous xanthoma disseminatum who developed central diabetes insipidus due to pituitary stalk involvement. Case Presentation: A 69-year-old male presented with a 2-year history of symmetrically distributed, erythematous to hyperpigmented macules and papules in the axillae and inguinal folds. He did not have any mucosal lesions. Skin biopsy revealed histiocytic infiltrate consistent with non-Langerhans cell histiocytosis, likely xanthoma disseminatum. He developed symptoms of polyuria and nocturia around the same time of the eruption, resulting in a large daily fluid intake of 100-120 ounces/day for several months. Laboratory evaluation revealed normal electrolytes. After an overnight water deprivation test, serum osmolality was 299mOsm/kg, serum sodium was 144mmol/L and urine osmolality was 280mOsm/kg, consistent with partial central diabetes insipidus. MRI pituitary with and without IV contrast showed thickening and hyperenhancement of the pituitary stalk. Anterior pituitary function was intact except for mild hypogonadotropic hypogonadism. He was started on DDAVP with good response and resolution of symptoms. Conclusion: Xanthoma disseminatum is characterized by extensive mucocutaneous xanthomatosis with occasional systemic involvement. The natural history of xanthoma disseminatum is usually benign, indolent, and slowly progressive with spontaneous regression described in a few cases. Hypothalamic and pituitary involvement may cause hyperprolactinemia, central diabetes insipidus, and variable degrees of hypopituitarism. Diabetes insipidus is often mild and sometimes transient. Occasionally, central diabetes insipidus can precede the skin lesions. Prognosis is generally good. Central nervous system involvement outside the hypothalamus/pituitary carries a poor prognosis. Presentation: 6/2/2024