An 11-year-old boy has experienced multiple bouts of severe abdominal pain for the past 6 years, but no other medical problems. His father and grandfather have been similarly affected. On examination during the last episode, bowel sounds were absent, and he exhibited marked diffuse abdominal pain with abdominal wall rigidity. A radiograph of the abdomen showed dilated loops of bowel with air-fluid levels. Laboratory studies showed serum amylase of 3320 U/L. This boy is most likely to have an inherited mutation involving which of the following genes?
□ (A) CFTR
□ (B) SMAD4
□ (C) K-RAS
□ (D) PRSS1
□ (E) SPINK1
