A 6-year-old Caucasian boy is brought to the office by his mother due to recurrent episodes of sinusitis. He also has a chronic cough that never seems to go away. The mother says that his previous pediatrician performed a "sweat test" to help determine the cause of his frequent infections, but results were normal. DNA testing was inconclusive. Despite these results, the new physician suspects that the patient has an inherited disorder and orders nasal transepithelial potential difference measurements. In this test, an isotonic solution of sodium chloride is applied to the nasal mucosal surface, and the electrical potential overlying the mucosa is compared with that of the interstitial fluid. The results show a transepithelial potential difference that is more negative than normal. This patient's nasal mucosa is most likely to demonstrate which of the following physiologic changes?

Question

A 6-year-old Caucasian boy is brought to the office by his mother due to recurrent episodes of sinusitis.  He also has a chronic cough that never seems to go away.  The mother says that his previous pediatrician performed a "sweat test" to help determine the cause of his frequent infections, but results were normal.  DNA testing was inconclusive.  Despite these results, the new physician suspects that the patient has an inherited disorder and orders nasal transepithelial potential difference measurements.  In this test, an isotonic solution of sodium chloride is applied to the nasal mucosal surface, and the electrical potential overlying the mucosa is compared with that of the interstitial fluid.  The results show a transepithelial potential difference that is more negative than normal.  This patient's nasal mucosa is most likely to demonstrate which of the following physiologic changes?

Quizplus · Accepted Answer

Eductional Objective: In cystic fibrosis, impairment of the cystic fibrosis transmembrane conductance regulator (CFTR) protein reduces chloride secretion and increases sodium absorption by the respiratory epithelia, resulting in dehydrated mucus.  When saline is applied to the nasal mucosa, the increased sodium absorption in patients with CF causes a more negative nasal transepithelial potential difference, which can be used to diagnose cystic fibrosis

A 6-Year-Old Caucasian Boy Is Brought to the Office by His