A 24-year-old man has recurrent sinusitis and bronchiectasis since childhood. Examination shows dextrocardia. Sperm analysis reveals immotile spermatozoa. Which ultrastructural defect best explains this presentation?

• A Mutation of the CFTR chloride channel
• B Defective alpha-1 antitrypsin folding in hepatocytes
• C Loss of elastic recoil from alveolar wall destruction
• D Absence of the dynein arms of microtubules ✓

Explanation

Kartagener syndrome is a variant of primary ciliary dyskinesia comprising situs inversus, bronchiectasis and sinusitis, caused by absent or defective outer dynein arms of the axonemal microtubules, which renders cilia and flagella immotile. Immotile sperm explains infertility. Cystic fibrosis causes bronchiectasis through airway mucus plugging rather than ciliary immotility, and it does not cause situs inversus.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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