A 1-year-old child presents with failure to thrive, frequent large voids of dilute urine, excessive

Discussion in 'MRCPCH forum' started by samuel, Sep 21, 2014.

  1. samuel

    samuel New Member

    A 1-year-old child presents with failure to thrive, frequent large voids of
    dilute urine, excessive thirst, and three episodes of dehydration not associated
    with vomiting or diarrhea. Over the years, other family members reportedly
    have had similar histories. Which of the following is the most likely diagnosis?
    a. Water intoxication
    b. Diabetes mellitus
    c. Diabetes insipidus
    d. Child abuse
    e. Nephrotic syndrome
  2. samuel

    samuel New Member

    Ans is C:
    nephrogenic diabetes insipidus is a hereditary disorder in which the urine is hypotonic and produced in large volumes because the kidneys fail to respond to antidiuretic hormone. Most North American patients thus involved are descendants of Ulster Scots who came to Nova Scotia in 1761 on the ship Hopewell. Males are primarily affected through an X-linked recessive inheritance causing inactivating mutation of the vasopressin V2 receptor; autosomal dominant and recessive forms are also known. The disorder is felt to result from primary unresponsiveness of the distal tubule and collecting duct to vasopressin. Although the condition is present at birth, the diagnosis is often not made until several months later, when excessive thirst, frequent voiding of large volumes of dilute urine, dehydration, and failure to thrive become obvious. Maintenance of adequate fluid intake and diet and use of saluretic medications (promoting the renal excretion of sodium) are the bases of therapy for this incurable disease.
    Acquired nephrogenic diabetes insipidus can be a result of lithium, methi-cillin, rifampin, and amphotericin. It may also be seen with hypokalemia,
    hypercalcemia, polycystic kidney disease, Sjögren syndrome, and sickle-cell disease.
    Water intoxication would not present with episodes of dehydration;
    diabetes mellitus rarely presents with a protracted course in such a young
    child (it is usually a more acute illness and often with vomiting). Child abuse would be unlikely, especially with a family history as noted. Nephrotic syndrome would be expected to present with other signs such as edema andproteinuria.

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