P-094 a Rare Cause of Polyuria and Polydipsia: Langerhans Cell Histiocytosis

Abstract Introduction Central diabetes insipidus is a clinical syndrome which results from loss or impaired function of ADH secreting neurons in the hypothalamus/posterior pituitary. The syndrome is characterized by hypotonic polyuria and compensatory polydipsia. It is estimated that destruction of over 90% of the vasopressinergic neurons is necessary for the clinical syndrome. Etiology of central diabetes insipidus involves trauma, autoimmunity, as well as inflammatory and infiltrative disorders. Langerhans cell histiocytosis (LCH) is a histiocytic disorder characterized by granulomatous lesions infiltrating various tissues and organs throughout the body. LCH is a rare diagnosis in adults occuring 0.07 per million annually. Pituitary may be involved in the multisystemic form of the disease and may present as diabetes insipidus. Here we present a case with polydipsia who was found out to have multisystemic LCH. Clinical Case A 35-year-old male patient was consulted to the endocrinology department for polydipsia. The patient had been well until three months before when he began drinking about 12 liters of water a day. He had been suffering from a slight pain in the left hip for four years that remained uninvestigated. He had a smoking history of 40 pack years. His medical history was otherwise unremarkable. Physical examination showed normal findings except a limited extension and external rotation of left hip. Laboratory tests revealed a urine osmolality of 60mOsm/kg and a serum osmolality of 287mOsm/kg. Water deprivation test was consistent with complete antidiuretic hormone (ADH) deficiency; central diabetes insipidus. Pituitary MRI showed a slight increase in the stalk thickness. Further investigation was carried out to understand the underlying disease. A high-resolution thorax computerized tomography (CT) showed peribronchial thickening, cystic enlargements and irregular reticular densities involving both upper lobes and superior segments of lower lobes. These findings suggested LCH. The bone scintigraphy demonstrated increased osteoblastic activity in right frontotemporal, posteroparietal and mandibular regions and trochanteric region of left femur. Positron emission tomography with fluorodeoxycholine showed; increased uptake in both lungs, right mandible, left femur, calvarium, right iliac bone and T2 vertebra. Bone biopsy from left femur proved the diagnosis of LCH. Desmopressin nasal spray was prescribed for ADH deficiency. Cladribine was started by the department of Hematology for Langerhans cell histiocytosis. Conclusion Central diabetes insipidus may be a sign of a multisystemic infiltrative or inflammatory disorder. Although rare, LCH should also be considered as an underlying disorder in CDI. Careful clinical and radiologic investigation is necessary for correct diagnosis and management.Figure 1:Fluoro-Deoxy Glucose- Positron Emission Tomography (FDG-PET) Table 1:Laboratory Results