primary ciliary dyskinesia
Summary
Primary ciliary dyskinesia (PCD) is a rare autosomal recessive disorder caused by defects in ciliary structure and function, leading to impaired mucociliary clearance. Classic triad includes chronic sinopulmonary infections, situs inversus (in ~50% of cases), and male infertility due to immotile sperm.
Detail
Primary ciliary dyskinesia results from mutations affecting dynein arms, radial spokes, or central pair structures within cilia and flagella. The most common defect involves outer dynein arms. Impaired ciliary beating leads to poor clearance of mucus and pathogens from respiratory tract, resulting in recurrent pneumonia, bronchiectasis, chronic otitis media, and sinusitis from birth. Kartagener syndrome represents the classic subset with situs inversus totalis (~50% of PCD patients), caused by defective nodal cilia during embryogenesis that normally establish left-right body asymmetry. Males typically have infertility due to immotile sperm flagella. Diagnosis involves nasal nitric oxide measurement (characteristically low), high-speed video microscopy of ciliary beating, and electron microscopy showing absent/shortened dynein arms. Treatment focuses on airway clearance, antibiotics for infections, and supportive care. Prognosis varies but progressive lung disease is common without proper management.
Sources
- First Aid for the USMLE Step 1
- Robbins Basic Pathology
- Nelson Textbook of Pediatrics
- Harrison's Principles of Internal Medicine
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