Paranasal sinus size is decreased in CFTR heterozygotes with chronic rhinosinusitis

Cystic fibrosis (CF) heterozygotes with a single mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene are at significantly higher risk to develop chronic rhinosinusitis (CRS). However the reasons why remain unknown. We tested the hypothesis that CFTR heterozygotes would have smaller sinus volumes than healthy controls. To exclude sinus disease as a confounding factor we also assessed paranasal sinus volume in those with CRS, but without known CFTR mutations.

A total of 131 adults of white Northern European and Latino origin were recruited: 81 diagnosed with CRS and 50 healthy controls. Subjects were genotyped for 9 common CFTR mutations covering >80% of mutation prevalence. Those with CRS were separated by CFTR mutational status and matched demographically to healthy controls. Three-dimensional sinus volume, mucosal opacification, and skull volume were quantified to obtain the percentage of pneumatization and extent of mucosal disease in each sinus. Twenty-item Sino-Nasal Outcome Test (SNOT-20) and endoscopy scores were also analyzed.

In individuals diagnosed with CRS we identified 7 CFTR heterozygotes (8.64%); no CFTR mutations were identified in our healthy controls. There were no significant differences between the 3 matched groups other than sinus pneumatization. The frontal and maxillary sinuses were significantly smaller in CFTR heterozygotes with CRS compared to CFTR wild-type subjects with or without disease.

CFTR heterozygotes with CRS have significantly smaller frontal and maxillary sinus size compared to those without mutations, irrespective of disease state. This sinus hypoplasia may contribute to impaired mucus clearance and chronic sinus disease development.