Patients with asthma who are cystic fibrosis transmembrane conductance regulator (CFTR) mutation carriers are more likely to experience recurrent neutrophilic bronchitis and eosinophilic bronchitis, according to a new study published in Allergy, Asthma & Clinical Immunology. The researchers also reported that hypertonic saline was effective in reducing exacerbations and was well-tolerated by patients.
“One potential cause of increased susceptibility to airway infections in asthma patients is [CFTR] hypofunction due to heterozygosity for a damaging CFTR mutation,” the authors explained. “A number of authors have reported that CF [cystic fibrosis] carriers are overrepresented in cohorts of certain respiratory diseases such as diffuse bronchiectasis, chronic rhinosinusitis, and asthma.”
The research team conducted a retrospective study on 75 patients with asthma who were referred for recurrent exacerbations between 2005 and 2020 in Canada. All the patients had CTFR mutation testing, and mutations were identified in 17.3%, a much higher percentage than expected given CTFR mutations have a 4% prevalence in the general population. The authors note that the high prevalence of CF carriers in this population contradicts the popular belief that CF carriers are asymptomatic.
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An association between CF carriers and older age and a higher number of exacerbations requiring hospitalization was also observed. The dominant sputum inflammatory subtype in this cohort was neutrophilic bronchitis, but more than half of the CF carriers also had eosinophilic bronchitis. In this patient cohort, nebulized hypertonic saline was well tolerated and effective in reducing the number of infective exacerbations.
Given that hypertonic saline works effectively in patients with CF to reduce the frequency of airway infections, the authors suspect it might be a more effective treatment for asthmatics who are CF carriers than for asthmatics who are noncarriers; however, this will require additional studies to confirm.
Priel E, Adatia A, Kjarsgaard M, et al. CFTR heterozygosity in severe asthma with recurrent airway infections: a retrospective review. Allergy Asthma Clin Immunol. Published online June 6, 2022. doi:10.1186/s13223-022-00684-0