Primary Ciliary Dyskinesia and Kartagener Syndrome
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Direct answer
Primary ciliary dyskinesia is an inherited, usually autosomal recessive disorder in which motile cilia are structurally defective, most often from dynein arm defects, so mucus cannot be cleared. When situs inversus, chronic sinusitis and bronchiectasis occur together, the combination is called Kartagener syndrome. Sperm tails are immotile, so most affected men are infertile. Diagnosis rests on low nasal nitric oxide and ciliary studies, and treatment is mainly airway clearance.
What you must remember
- Inheritance: usually autosomal recessive, caused by mutations in genes that encode ciliary structural proteins such as those forming the dynein arms.
- Ultrastructure: electron microscopy typically shows absent outer dynein arms, and high-speed video microscopy shows a slow or disorganised ciliary beat.
- Kartagener triad: situs inversus, chronic sinusitis and bronchiectasis. About half of patients with primary ciliary dyskinesia have situs inversus, and the rest have normal organ position.
- Screening test: markedly low nasal nitric oxide is a useful first screen, most reliable in cooperative patients aged about 5 years or more with a persistent wet cough, since values are less dependable in infants.
- Infertility: most men are infertile because sperm flagella are immotile, whereas women are often fertile, though fertility may be reduced and ectopic pregnancy risk is higher.
- Management: daily airway clearance physiotherapy, prompt antibiotics for exacerbations and long-term macrolides in selected patients. No drug reverses the ciliary defect.
A child with a wet cough and situs inversus
A 9-year-old boy has a wet cough since infancy, recurrent sinusitis and bronchiectasis on a high-resolution CT. A chest X-ray shows the heart on the right side, so ciliary dysfunction must be considered.
- Suspect the phenotype: Persistent neonatal respiratory distress in a term infant, a lifelong wet cough, chronic rhinosinusitis and bronchiectasis together point towards primary ciliary dyskinesia.
- Screen with nasal nitric oxide: A markedly low value raises suspicion, but it does not diagnose the disease on its own.
- Confirm ciliary function: High-speed video microscopy of nasal brushings shows an abnormal beat frequency or an abnormal beat pattern.
- Define the ultrastructure: Transmission electron microscopy looks for absent dynein arms or other axonemal defects, though a normal appearance does not always exclude the disease.
- Confirm genetically: Gene panels or exome sequencing identify causative variants, and DNAH5 and DNAI1 are among the commonest.
- Treat and monitor: Airway clearance, prompt antibiotics for exacerbations, serial lung function and counselling about fertility follow once the diagnosis is confirmed.
Where the examiner tests the Kartagener link
The exam separates the classic triad from look-alike situations, and the errors below are common.
- Trap: assuming every patient with situs inversus has primary ciliary dyskinesia Correct: isolated situs inversus is not PCD, but it needs cardiac evaluation because congenital heart disease can coexist.
- Trap: using a sweat chloride test to exclude the cause of bronchiectasis with sinus disease Correct: the test assesses cystic fibrosis, which is the main differential, and PCD needs ciliary and genetic testing.
- Trap: giving dornase alfa because it helps cystic fibrosis Correct: dornase alfa has no proven benefit in primary ciliary dyskinesia.
- Trap: treating the defect with mucolytics alone Correct: airway clearance and early antibiotics for exacerbations are the mainstays.
Frequently asked questions
Which test is the best initial screen for primary ciliary dyskinesia?
Low nasal nitric oxide is the most useful initial screening test for primary ciliary dyskinesia, most reliably in patients aged about 5 years or more who can cooperate. A low result must be followed by ciliary beat analysis and electron microscopy before the diagnosis is confirmed.
Why are men with primary ciliary dyskinesia usually infertile?
Men with primary ciliary dyskinesia are usually infertile because the same dynein defect makes sperm flagella immotile. Women with the condition are often fertile, although fertility may be reduced, so infertility is mainly a male problem.
Does dornase alfa help patients with primary ciliary dyskinesia?
Dornase alfa, the mucolytic that benefits cystic fibrosis, has no proven benefit in primary ciliary dyskinesia. Management relies instead on airway clearance physiotherapy, prompt antibiotics for exacerbations and long-term macrolides in selected patients.
What is the Kartagener triad?
The Kartagener triad consists of situs inversus, chronic sinusitis and bronchiectasis. It is a subset of primary ciliary dyskinesia, and situs inversus is found in about half of all patients with the disease.