Bronchiectasis patients with chronic rhinosinusitis have similar structural abnormalities in cilia — finger-like projections that help move mucus through the respiratory system — as those without this chronic inflammation of the upper respiratory tract, a study shows.
The study, “Prevalence of chronic rhinosinusitis in bronchiectasis patients suspected of ciliary dyskinesia,” was published in the International Forum of Allergy & Rhinology.
Cilia, structures located on the surface of cells in the respiratory tract, are the primary means by which the airways clear pathogens, allergens, debris, and toxins.
Primary ciliary dyskinesia (PCD) is a genetic condition that develops due to abnormal cilia, leading to poor mucociliary clearance — the removal of particles from the airways through mucus accomplished by the movement of cilia. Studies have shown that PCD can lead to bronchiectasis.
Acquired ciliary dysfunction is another condition marked by problems with how cilia work, but unlike PCD, it develops as a result of external factors (such as smoking) that alter ciliary structure, and interfere with cilia’s normal function.
Chronic rhinosinusitis (CRS) refers specifically to continuous inflammation of the sinuses that surround the nasal cavity (paranasal sinuses), a condition seen in most bronchiectasis patients (this study gives a range of 50% to 70%, another found it in up to 62% of them).
“Given the frequent association, it has been suggested that these 2 diseases [CRS and bronchiectasis] originate from a similar pathophysiologic mechanism,” the researchers wrote.
The team wondered if the common mechanism between these diseases could be the impairment of cilia, either through PCD or acquired ciliary dysfunction. Under this reasoning, structural abnormalities in cilia would be more evident in people with both bronchiectasis and CRS, compared to bronchiectasis alone.
To test their hypothesis, researchers at the University of Alabama at Birmingham conducted a study to investigate the connection between CRS, bronchiectasis, and the presence of any structural abnormalities in cilia due to either PCD or acquired ciliary dysfunction.
First, they examined the prevalence of CRS in adults with bronchiectasis being treated at their sinus clinic and suspected of ciliary defects. All were referred specifically for nasal brush biopsy (NBB), a technique used to sample ciliated epithelial cells that line the nasal tract.
Their study enrolled the 23 people (average age, 54) referred for an NBB.
Among them, 13 (56.5%) met the clinical criteria for a diagnosis of chronic rhinosinusitis, and 19 (82.6%) were found to have structural defects in the cilia. The most common defect was compound (fused) cilia, present in 11 (47.8%) patients.
DNA of 15 patients was analyzed for mutations in PCD-associated genes, and 60% (9 of 15) carried at least one gene associated with PCD. Only one patient, however, actually had been diagnosed with primary ciliary dyskinesia.
More than 85% of those with mutations in PCD-associated genes had structural abnormalities.
Researchers next looked for a potential connection between CRS and PCD.
Lund-Mackay scores (a widely used method for chronic rhinosinusitis staging) did not differ significantly between carriers of PCD-associated gene mutations and non-carriers. However, patients who carried multiple genetic mutations were found to have higher Lund-Mackay scores compared to those with a single or no mutation.
The team therefore suggested that “future higher powered studies investigating PCD gene carrier status as it relates to CRS may better delineate the role of genetics in disease pathogenesis.”
Researchers also found that about half (50%) of non-PCD gene carriers had a history of cigarette smoking. External factors like smoking may be related to acquired ciliary structural abnormalities, they wrote.
Specific analysis for a relationship between ciliary abnormalities, bronchiectasis, and CRS found none of significance. Ciliary abnormalities in bronchiectasis patients with CRS (84.6%) were not much greater than in those without chronic rhinosinusitis (80.0%).
“Nearly half of bronchiectasis patients referred for NBB had concurrent CRS,” the researchers concluded, but “the presence of ciliary abnormalities was not amplified in bronchiectasis patients with CRS, compared to those without CRS.”