A 4-year-old boy is brought to the office due to a progressively worsening cough for the past 2 days that is productive of yellow sputum. A year ago, he was found to have bilateral lower-lobe pulmonary infiltrates on chest x-ray and was diagnosed with pneumonia. The patient has since had 2 additional episodes of pneumonia, each requiring antibiotics for improvement of symptoms. His current chest x-ray again reveals bilateral lower lobe infiltrates. Further testing shows a high chloride content in his sweat. Which of the following abnormalities is most likely to be seen in this patient?

Question

A 4-year-old boy is brought to the office due to a progressively worsening cough for the past 2 days that is productive of yellow sputum.  A year ago, he was found to have bilateral lower-lobe pulmonary infiltrates on chest x-ray and was diagnosed with pneumonia.  The patient has since had 2 additional episodes of pneumonia, each requiring antibiotics for improvement of symptoms.  His current chest x-ray again reveals bilateral lower lobe infiltrates.  Further testing shows a high chloride content in his sweat.  Which of the following abnormalities is most likely to be seen in this patient?

Quizplus · Accepted Answer

Eductional Objective: Cystic fibrosis (CF) is most commonly due to a 3-base pair deletion in the CF transmembrane conductance regulator (CFTR) gene at amino acid position 508 ( F508).  This mutation impairs post-translational processing of CFTR, resulting in shunting of CFTR toward the proteasome, with complete absence of the protein on the cell surface.  Elevated sweat chloride concentrations are found in most patients with CF.

A 4-Year-Old Boy Is Brought to the Office Due to a Progressively