Immunoglobulin deficiencies in treated patients suffering from rheumatoid arthritis.

Immunoglobulins and antibodies to immunoglobulins (autoimmunoglobulins) have been identified to be implicated in the pathogenesis of rheumatoid arthritis (RA). Immunoglobulin deficiencies have been suggested to account for the increased risk of infections in RA patients. This study was carried out to determine the prevalence of immunoglobulin deficiencies in patients with RA and the identification of putative contributing factors. Immunoglobulin levels in blood samples of patients with rheumatoid arthritis were evaluated by an immunonephelometric assay. Demographic and disease related data (including age, sex, smoking habits, disease duration and activity, inflammatory markers) were assessed, and associations were identified by regression analysis. 539 patients were enrolled between 2011 and 2013. The most common immunoglobulin (Ig) deficiencies were those of IgM (24.5%) and IgG (19.9%). Most frequent deficiencies of subclasses were observed for IgG1 (42.3%), followed by IgG4 (10.4%), IgG2 (7.2%), and IgG3 (5.4%). Regression analyses revealed that deficiencies of IgM, IgG, IgG1, and IgG2 were more prevalent in older patients. In addition, smoking was associated with IgG2 deficiency, and IgA deficiency was associated with female sex. Occurrence of infections was significantly increased in patients with IgG, IgG2, and IgG4 deficiencies. RA patients displayed high rates of IgG and IgM deficiencies. In consequence, the assessment of immunoglobulin status should precede the application of immune modulating drugs to prevent a potential risk of infectious diseases. Prospective studies are needed to investigate the influence of immune modulating drugs on IgG and IgG subclass levels.