Persistent elevation of urine aquaporin-2 during water loading in a child with nephrogenic syndrome of inappropriate antidiuresis (NSIAD) caused by a R137L mutation in the V2 vasopressin receptor

International Journal of Pediatric Endocrinology

Stephen M Rosenthal¹  Stephen E Gitelman¹  Sayali A Ranadive³  Melissa A Cadnapaphornchai²  Clement C Cheung¹ 

[1] Department of Pediatrics, Division of Endocrinology, University of California, San Francisco, San Francisco, CA 94143;Department of Pediatrics, Division of Nephrology, University of Colorado Denver, Aurora, CO 80045;Pediatric Endocrinology, Palo Alto Medical Foundation, Fremont, CA 94538

关键词: Water Loading;    V2R;    NSIAD;    Aquaporin-2;   

Others  :  813585
DOI  :  10.1186/1687-9856-2012-3

 received in 2011-12-20, accepted in 2012-02-10,  发布年份 2012

【 摘 要 】

Nephrogenic Syndrome of Inappropriate Antidiuresis (NSIAD) is a novel disease caused by a gain-of-function mutation in the V2 vasopressin receptor (V2R), which results in water overload and hyponatremia. We report the effect of water loading in a 3-year old boy with NSIAD, diagnosed in infancy, to assess urine aquaporin-2 (AQP2) excretion as a marker for V2R activation, and to evaluate the progression of the disease since diagnosis. The patient is one of the first known NSIAD patients and the only patient with a R137L mutation. Patient underwent a standard water loading test in which serum and urine sodium and osmolality, serum AVP, and urine AQP2 excretion were measured. The patient was also evaluated for ad lib fluid intake before and after the test. This patient demonstrated persistent inability to excrete free water. Only 39% of the water load (20 ml/kg) was excreted during a 4-hour period (normal ≥ 80-90%). Concurrently, the patient developed hyponatremia and serum hypoosmolality. Serum AVP levels were detectable at baseline and decreased one hour after water loading; however, urine AQP2 levels were elevated and did not suppress normally during the water load. The patient remained eunatremic but relatively hypodipsic during ad lib intake. In conclusion, this is the first demonstration in a patient with NSIAD caused by a R137L mutation in the V2R that urine AQP2 excretion is inappropriately elevated and does not suppress normally with water loading. In addition, this is the first longitudinal report of a pediatric patient with NSIAD diagnosed in infancy who demonstrates the ability to maintain eunatremia during ad lib dietary intake.

【 授权许可】

   
2012 Cheung et al; licensee BioMed Central Ltd.

【 图 表 】

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