Perplexing Polyuria Caused by a Rare Disorder

Background: Central diabetes insipidus is an uncommon condition characterized by polyuria and polydipsia. In adults, central diabetes insipidus is most commonly caused by a primary brain tumor, followed by idiopathic causes, head trauma, and neurosurgery. The presence of diabetes insipidus is often discovered prior to the underlying culprit and detection may reveal further pituitary dysfunction. Herein an unusual cause of central diabetes insipidus is presented. Case: A 35-year-old male was seen in consultation for polyuria. He initially presented with fevers, cloudy urine, and excess urine output. He indicated frequent water consumption, craving cold water and feeling persistently dehydrated with poor energy levels. During hospitalization, the patient had up to 9 liters of urine output daily, with low urine osmolality and intermittent hypernatremia. As patients’ labs were consistent with central diabetes insipidus a brain MRI was completed and showed a thickened enhancing infundibulum and some fullness of the right pituitary without a focal lesion noted, concerning for autoimmune or inflammatory hypophysitis. Other pituitary axes were evaluated, and patient was noted to have a low morning total testosterone and low IGF-1. Concurrently, the patient was discovered to have multiple bone lesions on an MRI abdomen and pelvis, which prompted a bone scan showing diffuse uptake in osseous structures. A PET scan was then obtained demonstrating mandibular uptake as well as hypermetabolic activity in both adrenal glands, the right iliac bone, bilateral femurs and humeri. Biopsy of the mandibular lesion was performed, and the specimen revealed chronic xanthogranulomatous and lymphocytic inflammation consistent with a diagnosis of Erdheim-Chester disease. The patient was discharged on desmopressin and a biologic agent for treatment of Erdheim-Chester disease. Clinical Lesson: Erdheim-Chester disease is a rare non-Langerhans histiocytic multisystem disorder that often presents with skeletal, neurologic, endocrine, cutaneous, cardiac and renal abnormalities. There is a slight male predominance of the disorder and diagnosis occurs between the 5th and 7th decade of life. Erdheim-Chester disease is a form of histiocytosis with a histologic hallmark of xanthomatous infiltration of tissues by CD68-positive foamy histiocytes. This case reflects the diagnostic delay often associated with the condition. Early identification is essential to organize a multidisciplinary team to ensure accurate diagnosis and to initiate appropriate therapy. Presently interferon-alpha is the first line treatment, but other biologics are often used and provide promising outcomes. The presented case highlights many of the idiosyncrasies associated with this rare disorder and calls attention to the possibility of Erdheim-Chester disease when an initial cause of central diabetes insipidus is not obvious.