A 4-year-old boy is brought to the physician for a follow-up appointment. He has a history of recurrent bacterial pneumonias since the age of 6 months. He is at the 5th percentile for weight and height. The mother reports that her brother has a long history of not being able to conceive with his wife, where he produced a sample that showed “no sperm.” An x-ray of the child is shown.
Which of the following is the most likely explanation for these findings?
A) Decreased 7-dehydrocholesterol conversion into cholecalciferol
B) Decreased serum immunoglobulin concentrations
C) Decreased ENaC activity
D) Dynein arm defect
E) Exocrine pancreatic insufficiency
