Background: Diffuse alveolar hemorrhage (DAH) is associated with high mortality. We examined the efficacy of plasma exchange (PE) therapy for reducing mortality in patients with patients with microscopic polyangiitis (MPA) and DAH.

Methods: In this 52-week, nonrandomized, open-label, one-arm, historical control, double-center controlled trial, four patients with MPA and DAH admitted to Juntendo University Hospital or Juntendo Koto Geriatric Medical Center between 2018 and 2021 were enrolled. Sixteen patients with MPA and DAH admitted to the two centers between 1998 and 2018 who did not receive PE were included as the historical control group. The primary outcome was the 52-week survival rate of patients in each treatment arm.

Results: The 52-week survival rate of patients in the PE group (n = 4) was higher than that of the historical control group (n = 16) (100% vs. 13%, p = 0.04).

Conclusions: We found that PE may be efficacious for reducing mortality in patients with MPA and DAH.