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Cystic fibrosis — USMLE Step 3 MCQ

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EasyPediatrics (well-child, chronic management)Cystic fibrosisUSMLE Step 3

A 3-year-old child has recurrent sinopulmonary infections, chronic diarrhea, and failure to thrive. Sweat chloride is elevated. Which of the following is the most likely explanation for this patient's findings?

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Correct answer: A — Defective chloride transport causing dehydrated secretions

Cystic fibrosis results from defective CFTR chloride transport, leading to thick secretions in lungs, pancreas, and other organs.

Reference: Cystic Fibrosis Foundation guidance; USMLE Step 3 Content Outline