Pathology 9

1650.15 A 4-year-old boy is brought to the emergency department by his parents because of difficulty breathing and a cough productive of greenish sputum of several days' duration. Physical examination is notable for low-grade fever, respiratory rate 20/min, and hyperresonance to percussion, as well as scattered rales in the lung fields. Sputum cultures grow out Pseudomonas aeruginosa. A thorough history reveals that the child has had multiple hospitalizations for lung infections. His mother also reports that his newborn course was complicated by a period of vomiting and failure to pass stool, which resolved with an enema. Which of the following is the most likely underlying cause of this patient's chronic pulmonary disease?

Caucasian