A 25-year-old man presents with chronic productive cough, recurrent sinusitis, and infertility. Physical examination reveals situs inversus. Chest CT shows bilateral lower lobe bronchiectasis. The underlying genetic defect in this condition primarily affects which cellular structure?
- A CFTR chloride channel on chromosome 7
- B Alpha-1 antitrypsin production in hepatocytes
- C Dynein arm of cilia ✓
- D Elastase inhibition in neutrophils
Correct answer: C. Dynein arm of cilia
Explanation
The vignette describes Kartagener syndrome (primary ciliary dyskinesia) with the triad of bronchiectasis, sinusitis, and situs inversus. The defect is in dynein arms of cilia, causing immotile cilia. Option A is cystic fibrosis, which causes bronchiectasis but not situs inversus. Option D is the mechanism in alpha-1 antitrypsin deficiency, which causes emphysema, not bronchiectasis.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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