Pneumocystis jirovecii pneumonia in anti-MDA5-positive dermatomyositis: characterisation, risk factors and prognosis.

Objectives: This study aimed to identify risk and prognostic factors of Pneumocystis jirovecii pneumonia (PJP) in patients with anti-melanoma differentiation-associated gene 5 antibody-positive dermatomyositis (anti-MDA5+DM).

Methods: We conducted a retrospective cohort study of anti-MDA5+DM patients who underwent metagenomic next-generation sequencing analysis of bronchoalveolar lavage fluid or lung tissue at our center between January 2019 and February 2023. Eligible patients were stratified into PJP+ and PJP- groups based on PJP status. Potential risk factors and prognostic indicators for PJP were analysed using univariate and multivariate logistic regression analysis.

Results: A total of 107 anti-MDA5+DM patients were enrolled, of whom 47 were assigned to the PJP+ group. Multivariate logistic regression analysis revealed older age and high cumulative dosage of glucocorticoids within 3 months preceding PJP diagnosis were independent risk factors for PJP development. Conversely, prophylactic-dose trimethoprim-sulfamethoxazole (TMP/SMZ) was associated with a significantly reduced risk of PJP (all p<0.05). The 30-day mortality rate in the PJP+ group was 55.3%. Short disease duration and immunosuppressive therapy exposure, severe hypoxia, extensive radiological interstitial lung disease, moderate to severe acute respiratory distress syndrome, mechanical ventilation were associated with unfavourable prognosis (all p<0.05). Glucocorticoids therapy was more frenquently administered in survivors (p<0.05).

Conclusions: PJP significantly increases early mortality of anti-MDA5+DM patients. Clinicians should identify high-risk patients early and administer prophylactic-dose TMP/SMZ for PJP prophylaxis.