A Case of Idiopathic Central Diabetes Insipidus and a Mosaic Form of Turner Syndrome.

Central diabetes insipidus is a clinical syndrome caused by the loss of function of vasopressinergic neurons in the hypothalamus, which results in impaired secretion of arginine vasopressin (AVP). AVP deficiency leads to the inability to concentrate urine, resulting in hypotonic polyuria and polydipsia. The condition is most often acquired, but in some cases, the etiology remains unknown, in which the disease is classified as idiopathic. Turner syndrome is the most common sex chromosome abnormality in women, caused by complete or partial absence of one of the two X chromosomes. In some cases of Turner syndrome, an abnormal cell division occurs during the early stages of the fetal development, resulting in mosaicism: some cells in the body possess two complete copies of the X chromosome, while others have only one. The coexistence of Turner syndrome and diabetes insipidus is extremely rare but should nevertheless be sought in all patients through focused clinical thinking and testing, as both conditions have long-term health consequences and should be promptly diagnosed and treated. We report a clinical case of a 22-year-old female patient, diagnosed with idiopathic central diabetes insipidus and a mosaic form of Turner syndrome, presenting with polyuria and polydipsia. The performed water deprivation and desmopressin tests proved a central form of diabetes insipidus. The imaging studies that were conducted, an MRI of the hypothalamic-pituitary region in particular, revealed the existence of a "dark" type microadenoma with discrete compression of the infundibulum. The patient was started on vasopressin replacement treatment with a good therapeutic effect. In the follow-up imaging studies, the structure of the pituitary gland showed no dynamics. There are only a few cases of simultaneous development of central diabetes insipidus and Turner syndrome that have been described in the literature. Further research is needed in order to discover the connection between the pathogenesis of the development of antidiuretic hormone deficiency and Turner syndrome.