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. To investigate the prevalence and mortality rate of PJP infection in subgroups of IIM patients stratified according to myopathy-specific antibodies. 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. 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). 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.

中文翻译：

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抗 MDA5 抗体阳性皮肌炎肺囊虫感染的高发病率和死亡率：来自单一中心的经验

特发性炎症性肌病 (IIM) 与机会性感染的风险显着升高相关，包括吉氏肺孢子菌肺炎 (PJP)，一种可能致命的机会性感染。然而，之前没有研究评估 IIM 亚型中的 PJP 感染。调查根据肌病特异性抗体分层的 IIM 患者亚组中 PJP 感染的患病率和死亡率。在研究的第一部分，对 463 名连续 IIM 患者进行了至少 1 年的前瞻性随访，以分析 PJP 的发生率。在研究的第二部分，我们连续招募了 30 名患有任何风湿病的 PJP 患者，以便通过 Cox 回归分析确定死亡率和危险因素。采用对数秩检验的 Kaplan-Meier 方法用于评估生存差异。IIM 患者 PJP 的患病率为 3.0/100 人年，而 MDA5+ DM 患者为 7.5/100 人年，MDA5-IIM 患者为 0.7/100 人年（P < 0.05）。PJP 通常发生在 MDA5+ DM 患者的前 2 个月，其 CD4+ T 细胞计数和淋巴细胞计数显着减少（P < 0.05）。在 PJP 患者中，MDA5+ DM 患者的 3 个月死亡率高于其他风湿性疾病患者（83.3% vs 38.9%，P < 0.05）。令人担忧的是，与其他风湿病患者在 6 天内开始抗 PJP 治疗时生存率提高的其他风湿病患者不同，MDA5+ DM 患者似乎并未从及时的抗 PJP 治疗中受益（P < 0.05）。PJP 在 MDA5+ DM 患者中具有惊人的高发病率和死亡率。PJP 的及时治疗似乎不能改善这种特定亚型患者的预后。因此，仍然存在为 MDA5+ DM 患者开发 PJP 预防的关键未满足需求。