This study aimed to evaluate the clinical significance of maxillary sinus hypoplasia and isolated agenesis of the uncinate process in sinusitis aetiology.

Three patients with isolated agenesis of the uncinate process and 27 patients with 43 maxillary sinus hypoplasia variations were recruited. The frequencies of sinusitis episodes and radiological findings were compared between patient subgroups.

In all, 23 type I maxillary sinus hypoplasia, 13 type II maxillary sinus hypoplasia and 7 type III maxillary sinus hypoplasia variations were detected. Patients with isolated agenesis of the uncinate process underwent antibiotic treatment an average of 7 times per year, whereas those with types I, II and III maxillary sinus hypoplasia were treated 1.57, 3.22, and 5.75 times per year, respectively, over a 5-year period. The antibiotic treatment frequency for patients with isolated agenesis of the uncinate process was significantly higher than for those with types I and II maxillary sinus hypoplasia.

Isolated agenesis of the uncinate process seems to play a stronger role than types I and II maxillary sinus hypoplasia in the pathophysiology of chronic sinusitis.