Pediatric patients with likely primary ciliary dyskinesia frequently have asthma

Scott D. Sagel, MD, PhD

PCD is a rare, genetic disorder characterized by defective beating of motile cilia (tiny, hair-like projections that extend from the surface of cells in the respiratory tract), leading to impaired mucus clearance, persistent airway infections and chronic airway inflammation, and bronchiectasis. Asthma is a far more common chronic lung condition, affecting approximately 8% of the U.S. population.

It is challenging to determine whether children with PCD also have asthma, as both disorders are characterized by coughing, wheezing and airflow obstruction on lung function testing. Findings from this case-control study from two large electronic health record-based databases suggest that most children with PCD also have a concomitant diagnosis of asthma.

These findings align with our clinical experience. Approximately 80% of children with PCD followed longitudinally through our NIH-funded Genetic Disorders of Mucociliary Clearance Consortium report using daily asthma controller therapies including inhaled corticosteroids (ICS) alone or in combination with long-acting beta-agonists.

Also, prior research has found that over 50% of children with PCD have evidence of reversible airflow obstruction (significant improvement in airflows following a bronchodilator treatment) that is a characteristic finding in people with asthma. Interestingly, reversible airflow obstruction in children with PCD does not appear to be associated with a personal or family history of asthma or allergies.

The reason that we see a high frequency of reversible airflow obstruction and often prescribe ICS to children with PCD remains unclear. These authors believe that impaired ciliary movement leads to antigen stasis on the airway surface (allergens or substances that stick to the airways), which stimulates an inflammatory response and predisposes these children to also having asthma. There is likely something unique about the airway environment that leads to asthma features in children with PCD.

The main limitation to note is that the children in these databases had a presumed diagnosis of PCD, not a confirmed diagnosis, based on having the combination of bronchiectasis and situs inversus totalis, which are unlikely to occur together in the absence of PCD.

The effectiveness of ICS alone or in combination with LABA therapy should be more carefully studied in children with PCD. Also, we need more research on the immune responses and inflammation in the PCD airway.

Asthma appears to be a relatively common comorbidity and should be considered among children with PCD. These findings, and the presence of reversible airflow obstruction in their own patients, should direct doctors to consider a diagnosis of asthma and prescribe asthma medicines, including ICS, in children with PCD.