Erosion of the lateral nasal wall is assumed to be due to osteitis or the pressure exerted by polyps or thick mucus on the medial wall of the sinus, leading to the formation of "pseudomucocele" (Figure 2).(13) In pediatric patients, the aforementioned changes should raise the suspicion of CF.(14) One study showed that patients homozygous for ΔF508 were more likely to have frontal, maxillary, and sphenoid sinus hypoplasia than were those with other mutations in the CFTR protein.(14). The gene discussed is CFTR; the disease is cystic fibrosis.