A 16 month old child was brought to Pediatric OPD . Child's mother informed doctor told that child is always thirsty, and she has to change his diapers frequently. She also states that he passes large voids of urine. On examination child appears dehydrated but there is no history of vomiting or diarrhoea. Which of the following is the most likely cause?

Nephrogenic diabetes insipidus: inherited disorder leading to mutation of the vasopressin V2 receptor. Hypotonic urine produced in large volumes because of unresponsiveness of the distal tubule and collecting duct to ADH. C/F: excessive thirst, frequent large voids of urine, dehydration, and failure to thrive. Management: adequate fluid intake and diet and use of saluretic medications Water intoxication does not present with episodes of dehydration. Diabetes mellitus is usually a more acute illness and often with vomiting. Nephrotic syndrome presents with other signs like edema and proteinuria.