A 3-month-old boy is brought to the office because he is fussy, not gaining weight, and has polyuria. The daily urine volume is 700-800 mL. Polydipsia and polyuria are symptoms of the patient's maternal grandfather. Serum sodium concentration is 151 mEq/L. A vasopressin-2 receptor mutation is discovered through genetic testing. Which of the following additional findings in this patient is most likely?

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Quizplus · Accepted Answer

Eductional Objective: Vasopressin-2 receptor mutations are a cause of congenital nephrogenic diabetes insipidus, a condition characterized by renal resistance to antidiuretic hormone and excessive urinary water loss. High baseline serum osmolality (typically associated with hypernatremia), persistently dilute urine after water deprivation (low urine osmolality), and lack of response to desmopressin are all expected findings.

A 3-Month-Old Boy Is Brought to the Office Because He