Serum immunoglobulins and IgG subclass levels in adults with chronic sinusitis: Evidence for decreased IgG3 levels

Serum immunoglobulin class and IgG subclasses were measured in 30 adult patients with chronic sinusitis documented by CT scans of the paranasal sinuses. Results were compared to 30 age-and-sex matched patients with chronic rhinitis who had normal sinus CT scans, and a matched group of asymptomatic, healthy subjects. None of the patients was taking oral corticosteroids and none had ever received allergen immunotherapy. IgA deficiency was present in 3% (2/60) of the patients with chronic rhinitis or sinusitis and IgG deficiency was seen in another two (3%). None of the normals had low IgA or IgG. Low levels of IgG1 or IgG3 were found in some patients in all three groups, while none had low IgG2 levels. Serum levels of IgG, IgA, IgM, IgG1, IgG2, and IgG4 were not significantly different between the groups. Mean serum IgG3 levels, however, were significantly lower in the chronic sinusitis group than the chronic rhinitis group (P < .003) or the normals (P < .0005). The incidence of below normal levels of IgG3 was also more frequent in chronic sinusitis than in chronic rhinitis (P < .04) or normals (P < .002). Patients in the chronic sinusitis group had a high incidence of asthma (57%) and atopy (45%) but there was no difference in immunoglobulin class or IgG subclass levels in matched asthmatics compared with nonasthmatic patients with chronic sinusitis. Atopic patients with chronic sinusitis had a higher frequency of IgG3 subclass deficiency than nonatopics (P = .04). Normalization of low immunoglobulin class or IgG subclass levels that coincided with clinical improvement was documented in two patients with sinusitis. These findings indicate that IgG3 levels are significantly decreased in adults with chronic sinusitis independent of oral corticosteroid use. This may be a secondary phenomenon since low IgG3 levels may normalize with time.