Primary ciliary dyskinesia — formative SAQs

SAQ 1 — The preschooler with a lifelong wet cough and situs inversus (20 marks, ~15 minutes)

A 4-year-old girl is referred with a wet cough that her parents say has been present on most days since she was a few weeks old. She had unexplained respiratory distress as a term newborn, has a constantly runny nose, and has had recurrent glue ear with two sets of grommets. A chest radiograph incidentally shows the heart on the right side. [4]

Questions

1. Give the most likely diagnosis and the features in this history that support it. (6 marks) [4]
2. Name the single most important alternative diagnosis to exclude and how you would exclude it. (4 marks) [2]
3. Outline the diagnostic pathway you would use to confirm the diagnosis. (6 marks) [1]
4. Explain why a normal chest radiograph and normal organ position would not exclude the diagnosis in another child. (4 marks) [4]

Model answer (must-hit)

1. The most likely diagnosis is primary ciliary dyskinesia, in this child specifically Kartagener syndrome because situs inversus is present. Supporting features are the daily wet cough present since the first weeks of life, unexplained neonatal respiratory distress in a term infant, chronic year-round rhinorrhoea, recurrent otitis media with effusion needing grommets, and dextrocardia indicating situs inversus. [4]
2. The single most important alternative to exclude is cystic fibrosis, because it is the other leading genetic cause of early-onset wet cough and bronchiectasis. It is excluded with a sweat chloride test and, where indicated, cystic fibrosis genetic testing, remembering to also assess for pancreatic insufficiency and faltering growth. [2]
3. The diagnostic pathway is performed in a specialist centre and combines tests because none is sufficient alone: nasal nitric oxide as a screen (characteristically very low), high-speed video microscopy of a nasal brushing to assess ciliary beat frequency and pattern, transmission electron microscopy for ultrastructural defects such as absent dynein arms, and genetic panel testing, with immunofluorescence as an adjunct. [1]
4. Normal organ position does not exclude PCD because the laterality defect is present in only about half of affected children; the other half have normal situs and identical airway disease. The diagnosis therefore rests on the clinical phenotype and the specialist diagnostic tests rather than on organ position. [4]

SAQ 2 — The school-aged child with confirmed PCD and early bronchiectasis (20 marks, ~15 minutes)

An 8-year-old boy with genetically confirmed primary ciliary dyskinesia has a daily productive cough, early bronchiectasis on imaging, and a recent sputum culture growing Pseudomonas aeruginosa for the first time. His lung function is beginning to decline. [5]

Questions

1. Outline the cornerstone of his long-term management and why it matters. (5 marks) [5]
2. State how you would approach his airway infection, including the new Pseudomonas. (7 marks) [5]
3. State the role and evidence for maintenance azithromycin in PCD. (4 marks) [9]
4. List the additional multidisciplinary components of his care. (4 marks) [1]

Model answer (must-hit)

1. The cornerstone is daily airway clearance physiotherapy supported by regular exercise, because it mechanically substitutes for the clearance the cilia cannot provide. Adherence to daily clearance is the single most important determinant of preserved lung function over time, so establishing and supporting it is central to preventing further decline. [5]
2. Infection is managed by regular surveillance airway cultures, prompt treatment of exacerbations with antibiotics directed by the isolated organisms, and active eradication of newly isolated Pseudomonas aeruginosa rather than allowing it to become chronic, using an eradication protocol adapted from cystic fibrosis and bronchiectasis care and intensifying airway clearance alongside. [5]
3. Maintenance azithromycin is used as prophylaxis to reduce exacerbations in selected children. The BESTCILIA randomised controlled trial, the landmark PCD-specific trial, showed that regular azithromycin roughly halved the rate of respiratory exacerbations; non-tuberculous mycobacterial infection should be excluded before starting and it supplements rather than replaces airway clearance. [9]
4. Additional components are monitoring of lung function and imaging, ENT and audiology care for chronic otitis media and hearing loss, current immunisations including influenza, avoidance of tobacco smoke, nutrition and growth monitoring, genetic counselling for the family, and psychosocial support with planned transition to adult services. [1]