Mucosal thickening in allergic and idiopathic rhinitis mucosa and its probable mechanism

Background: Rhinitis is a prevalent condition characterized by nasal mucosal irritation. Conflicting studies suggest that the mucosa of patients with allergic and nonallergic rhinitis undergoes thickening. Objectives: To investigate mucosal epithelial thickening in allergic and idiopathic rhinitis and to determine if the mechanism is a consequence of altered proliferation or apoptosis. Methods: Interactive image analysis was performed on histologic sections of inferior nasal turbinate tissue to measure epithelial thickness in 3 patient groups. Patients with allergic rhinitis (n = 15), patients with idiopathic rhinitis (n = 15), and a healthy control group (n = 10) were compared. Immunohistochemical and morphometric analyses were used to quantify cell proliferation (Mib-1), apoptosis (terminal uridine nick end labeling technique), and the antiapoptotic factor Bcl-2. Results: Idiopathic epithelium was found to be significantly thickened compared with healthy epithelium (P = .04). Epithelial thickening occurred in some allergic patients, but the findings did not reach statistical significance (P = .22). No statistically significant difference in proliferation as evidenced by Mib-1 staining was seen among the 3 patient groups. Allergic mucosa differed statistically significantly to that of patients with idiopathic rhinitis (P = .01) and healthy controls (P = .005) in showing increased Bcl-2 staining, suggesting reduced apoptosis. Conclusions: Allergic epithelium shows significantly decreased apoptosis, which might explain the increased epithelial thickening seen in some study participants. This mechanism does not, however, appear to explain the significantly increased thickening, seen in the idiopathic epithelium. Furthermore, both allergic and nonallergic epithelium showed regional thinning and thickening possibly involving an inflammatory infiltrate. Ann Allergy Asthma Immunol. 2009; 103:14-19.