Comparison of the Clinical Characteristics of Pneumocystis Pneumonia between Patients with Rheumatoid Arthritis Being Treated with Biologics and Those Being Treated without Biologics

Objective. The aim of this study was to compare the clinical characteristics of pneumocystis pneumonia (PCP) between patients with rheumatoid arthritis (RA) being treated with biologics and those being treated without biologics. Methods. From 8,630 patients with RA in our institution, we enrolled 24 patients who had developed PCP during the course of their treatment. They were divided into two groups according to the treatment they were receiving for RA: the biologics group (n=12) and the nonbiologics group (n=12). Clinical characteristics of PCP were compared between the two groups. Results. At PCP diagnosis, the biologics group showed significantly lower serum levels of β-D-glucan and C-reactive protein than the nonbiologics group, while the biologics group had significantly higher lymphocyte counts than the nonbiologics group. In the nonbiologics group, lower lymphocyte counts were associated with higher β-D-glucan levels; however, this was not observed in the biologics group. Conclusion. The finding that RA patients being treated with biologics developed PCP with relatively normal lymphocyte counts and lower β-D-glucan levels suggests that the pathophysiology of PCP in those patients is different from that in patients being treated with other antirheumatic drugs.