Hyponatremic dehydration as a presentation of cystic fibrosis

Background: The purpose of this study is to present a case report of a child with hyponatremic dehydration diagnosed after CF and to review the cases of 13 patients with CF who had the same initial presentation in our hospital. Methods: This report reviewed the clinical records of children diagnosed with CF to ascertain the prevalence of metabolic alkalosis with electrolyte depletion as the presentation of CF. It also used sweat tests to diagnose a child with CF. Results: The laboratory tests of a 12-month-old girl presented 3 times to the pediatric emergency department with vomiting and weight loss showed hyponatremia, hypochloremia, and metabolic alkalosis. The patient was subsequently diagnosed with CF by means of 2 positive sweat tests. Meanwhile, the review of the clinical records of all children diagnosed with CF from 1985 to 2004 (N = 77) showed that the prevalence of metabolic alkalosis with electrolyte depletion as the presentation of CF was 16.8%. The age of the infants ranged from 3 to 14 months. All episodes took place during summer. Conclusions: There are not many causes of metabolic alkalosis with hyponatremic dehydration, and one of them is CF. This report emphasizes sodium depletion as a common sign of CF presentation. This is most important in countries where the neonatal screening test for CF is not available because the disease may be asymptomatic or oligosymptomatic for several months or even years. Cystic fibrosis should be considered in differential diagnosis of any child presenting with unexplained hyponatremic dehydration.