Risk factors for severe infections during induction therapy of patients with microscopic polyangiitis

Severe infections contribute to morbidity and mortality in microscopic polyangiitis (MPA). This study aims to investigate the clinical characteristics and identify risk factors for early severe infections in newly diagnosed patients with MPA.

This retrospective cohort study included patients newly diagnosed with MPA followed up for at least 6 months at two tertiary care centres between January 2013 and December 2023. Clinical data, including demographics, laboratory findings, treatment regimens, and infection details, were collected. Multivariable logistic regression analysis was used to identify risk factors for severe infections within 6 months after the diagnosis in patients with new-onset MPA.

A total of 374 patients with MPA were included, and 25.9% (97/374) experienced severe infections. Compared to the non-infection group, the infection group had a significantly higher daily average dosage of prednisone for remission induction, a higher proportion of patients with a history of chronic lung disease, and a higher proportion receiving rituximab (RTX) therapy (p<0.05). In multivariable logistic regression analysis, a history of chronic lung disease, higher daily average dosage of prednisone therapy and RTX therapy for remission induction were associated with an increased risk of severe infections, whereby higher baseline serum IgM levels were associated with a decreased risk. The most common site of infection was the lung (75.23%), and bacteria (43.1%) was the most prevalent pathogen.

MPA is associated with a high risk of severe infections, especially in patients treated with higher dosage glucocorticoid and with a history of chronic lung disease.