Primary Ciliary Dyskinesia

Respiratory Cilia

Found lining the conducting airways from the nasal cavity down to the terminal bronchioles.
The epithelium is pseudostratified ciliated columnar epithelium.
Note: Cilia are absent in the alveoli and respiratory bronchioles (gas exchange zones).

Arrangement: Characterized by the classic "9 + 2" microtubular arrangement.
- 9 peripheral microtubule doublets.
- 2 central single microtubules.
Key Components:
- Dynein Arms (Inner & Outer): ATPase motor proteins attached to microtubules that generate force for movement. Defects here cause PCD.
- Radial Spokes: Connect peripheral doublets to the central sheath.
- Nexin Links: Elastic proteins connecting adjacent doublets.

Mucociliary Clearance (The "Escalator"): Cilia beat in a coordinated, rhythmic wave (Metachronal rhythm) at 10–15 Hz.
Mechanism: They propel the overlying mucus layer (trapping dust, bacteria, and debris) cephalad (towards the pharynx) to be swallowed or expectorated.
Host Defense: Primary innate defense mechanism preventing lower respiratory tract infections.

Definition: A genetically heterogeneous, autosomal recessive disorder characterized by abnormal ciliary structure or function, leading to impaired mucociliary clearance.
Incidence: 1 in 15,000 – 30,000.
Kartagener Syndrome: A subgroup of PCD (~50%) characterized by the triad:
1. Situs Inversus.
2. Chronic Sinusitis.
3. Bronchiectasis.

Symptoms often begin in the neonatal period and persist.

Neonatal Period (High Index of Suspicion):
- Unexplained Respiratory Distress: Term infant requiring $O_{2}$ without risk factors (e.g., Meconium, sepsis).
- Neonatal Rhinitis: Continuous nasal discharge from birth.
Childhood & Adolescence:
- Respiratory:
  - Chronic Wet Cough: Daily, year-round, starting in infancy.
  - Recurrent Pneumonia: Leading to early Bronchiectasis (lower lobes).
  - Intractable Asthma: "Difficult asthma" unresponsive to treatment.
- ENT:
  - Chronic Rhinosinusitis: Nasal polyps are rare (unlike CF) but congestion is constant.
  - Chronic Otitis Media with Effusion (OME): Conductive hearing loss is almost universal.
- Situs Abnormalities: Situs inversus totalis or situs ambiguus (heterotaxy).
Adulthood:
- Infertility:
  - Males: Immotile sperm (sperm flagella have same 9+2 structure).
  - Females: Risk of ectopic pregnancy (tubal cilia dysfunction) or subfertility.

Diagnosis is challenging and requires a tiered approach.

Screening Test:
- Nasal Nitric Oxide (nNO): Levels are extremely low (<77 nL/min) in PCD (cilia regulate NO production). Gold standard screening test in children >5 years.
Confirmatory Tests:
1. High-Speed Video Microscopy (HSVM): Analyzes ciliary beat frequency and pattern from nasal brush biopsy.
2. Transmission Electron Microscopy (TEM): Visualizes structural defects (e.g., absent dynein arms).
3. Genetic Testing: Panels testing for DNAH5, DNAI1 (common mutations).

There is no curative therapy. Management is supportive, largely adapted from Cystic Fibrosis protocols.

A. Airway Clearance (The Cornerstone)

Chest Physiotherapy: Twice daily percussion/vibration or oscillatory PEP devices (Flutter/Acapella).
Exercise: Encouraged to promote deep breathing and cough.

B. Infection Control

Surveillance: Routine sputum cultures (every 3 months).
Antibiotics:
- Acute Exacerbations: Aggressive treatment (Oral/IV) for 14–21 days.
- Prophylaxis: Long-term Azithromycin (anti-inflammatory + antibacterial) is often used.
- Nebulized Antibiotics: For chronic Pseudomonas colonization.

C. ENT Management

Hearing: Hearing aids are often preferred over grommets (ventilation tubes) because grommets often have persistent purulent discharge in PCD.
Sinusitis: Saline nasal douches and nasal steroids.

D. Monitoring

Generally better than Cystic Fibrosis.
Slow decline in lung function; end-stage lung disease may require transplantation in adulthood.