Случай нефрогенного синдрома неадекватного антидиуреза, обусловленный мутацией рецептора вазопрессина 2-го типа

Nephrogenic syndrome of inappropriate antidiuresis (NSIAD) is a rare X-linked disorder of water balance, which was first described in two unrelated male infants with severe symptomatic hyponatremia. NSIAD is caused by activating mutations of the arginine vasopressin receptor 2 ( AVPR2 ) gene, resulting in impaired reabsorption of free water, which leads to increased osmolarity of urine, plasma hypo-osmolarity, and persistent hyponatremia. We report, for the first time in the domestic literature, a case of isolated euvolemic hyposmolality hyponatremia in a child with oligodipsia. Because hypocorticism and renal pathology were excluded, and there was no antidiuretic hormone hypersecretion, NSIAD was suggested. A molecular genetic study revealed a new mutation L312S, not described earlier, in the seventh transmembrane domain of the AVPR2 gene. Pathogenicity of the mutation was proved by a functional study. We provide the clinical and laboratory characteristics of SIAD and the main principles of treatment. This disease should be considered in the differential diagnosis of hyponatremia syndrome.