UNLABELLED: HYPOTHESES/OBJECTIVES:: In adults, purulent pansinusitis or nasal polyposis starting early in life or that is permanently infected or associated either with chronic bronchial infection, infertility, or situs inversus are uncommon. In these atypical cases of chronic sinusitis (ACS), a primary dysfunction of the mucociliary clearance can be suspected. Adult patients with ACS were therefore investigated to detect primary ciliary dyskinesia (PCD) or cystic fibrosis (CF). STUDY DESIGN: Open, prospective study. PATIENTS AND METHODS: Forty-two patients with ACS were investigated with ciliary beat frequency and ultrastructure analysis in nasal cells and cystic fibrosis transmembrane conductance regulator (CFTR) gene mutation analysis in blood leukocytes. RESULTS: The diagnosis of PCD was confirmed in seven (17%) patients. At least one CFTR gene mutation was detected in 16 (38%) patients. The diagnosis of CF was suggested in three (7%) compound heterozygous patients. Another 13 (31%) patients were heterozygous for a CFTR gene mutation or a complex allele. Comparison of clinical features of ACS showed that only a family history of chronic sinusitis (P <.01) or chronic bronchitis (P <.02) and the presence of diffuse bronchiectasis (P <.0001) or serous otitis media (P <.0001) were significantly more frequent in PCD patients than in patients carrying CFTR gene mutations or those without PCD or CFTR gene mutations. CONCLUSIONS: ACS should be considered a remarkable entity in which congenital abnormalities of epithelial cells are frequently detected (55% of patients). The higher frequency of mutations in ACS patients compared with the general population suggests that heterozygoty for CFTR gene mutation could be a sinusitis-causing status.