High incidence and mortality of Pneumocystis jirovecii infection in anti-MDA5-antibody-positive dermatomyositis: experience from a single center

Background Idiopathic inflammatory myopathies (IIM) are associated with a significantly higher risk of opportunistic infections including Pneumocystis jirovecii pneumonia (PJP), a potentially fatal opportunistic infection. However, no prior studies have evaluated PJP infection in subtypes of IIM. Objectives To investigate the prevalence and mortality rate of PJP infection in subgroups of IIM patients stratified according to myopathy-specific antibodies. Methods In the first part of the study, 463 consecutive patients with IIM were prospectively followed for a period of at least 1 year to analyze the incidence of PJP. In the second part of the study, we enrolled 30 consecutive PJP patients with any rheumatic disease in order to identify the mortality rate and risk factors by Cox regression analysis. The Kaplan-Meier method with log-rank testing was used to assess differences in survival. Results The prevalence of PJP in IIM patients was found to be 3.0/100 person-years, while in MDA5(+) DM patients it was 7.5/100 person-years and in MDA5(-) IIM patients 0.7/100 person-years (P < 0.05). PJP typically occurred in the first 2 months in the case of MDA5(+) DM patients who had a significant decrease in their CD4(+) T cell counts and lymphocyte counts (P < 0.05). In PJP patients, 3-month mortality was higher for MDA5(+) DM patients than in those with other rheumatic diseases (83.3% vs 38.9%, P < 0.05). Alarmingly, MDA5(+) DM patients seemed not to benefit from prompt anti-PJP treatment, unlike patients with other rheumatic diseases whose survival improved when anti-PJP treatment was started within 6 days (P < 0.05). Conclusion PJP has an alarming high incidence and mortality in MDA5(+) DM patients. Timely treatment for PJP seems not to improve the prognosis of patients with this particular subtype. Hence, there remains a crucial unmet need to develop PJP prophylaxis for MDA5(+) DM patients.