Background Cases with Pneumocystis pneumonia (PCP) have been reported in patients with rheumatoid arthritis, mainly treated with biologics. An experimental study in the mouse revealed that sulfasalazine enhances the clearance of the Pneumocystis organism from the lung (1). Furthermore, a case-control study with small sample size indicated possible preventive effect of sulfasalazine against PCP (2).

Objectives The aim of this study is to clarify the prophylactic effect of sulfasalazine against PCP in patients with rheumatoid arthritis with a large sample size.

Methods This retrospective study focused on all patients with rheumatoid arthritis seen between April, 2011 and October, 2016. at department of rheumatology, Tokyo Metropolitan Tama Medical Center. We investigated their demographics and medication, including corticosteroids, disease-modifying antirheumatic drugs and prophylactic drugs against PCP. The person-time at risk was calculated from prescription records. We compared the incidence during the period of follow-up in which the patients received sulfasalazine with that in which they did not received sulfasalazine. The incidents were assumed to follow a Poisson distribution and statistical analysis was performed using z-test.

Results In the study period, 2,394 patients with rheumatoid arthritis were treated at our hospital. Among them, 24 patients received the treatment for PCP because the infection was diagnosed or was strongly suspected. All the cases developed the condition while they were not taking sulfasalazine. The incidence rate of PCP was significantly lower in the treatment period with sulfasalazine than that without sulfasalazine (p<0.001).

Conclusions Our study confirmed that sulfasalazine has a preventive effect against PCP in patients with rheumatoid arthritis.

References

1. Wang J, Gigliotti F, Bhagwat SP, George TC, Wright TW. Immune modulation with sulfasalazine attenuates immunopathogenesis but enhances macrophage- mediated fungal clearance during pneumocystis pneumonia. PLoS Pathog. 2010;6(8):59–60.

2. Mizushina K, Hirata A, Hayashi N, et al. Possible preventive effect of salazosulfapyridine against development of Pneumocystis pneumonia in methotrexate-receiving patients with rheumatoid arthritis. Mod Rheumatol. 2015;7595(November):1–8.

References

Disclosure of Interest None declared