Rituximab for double-positive anti-GBM antibody and ANCA-associated glomerulonephritis: The first reported case in Asia and literature review.

Background: Double-positive patients exhibit both anti-glomerular basement membrane antibody and anti-neutrophil cytoplasmic antibody. Its initial treatment includes induction cyclophosphamide, glucocorticoids, and plasmapheresis, followed by maintenance therapy similar to that for anti-neutrophil cytoplasmic antibody-associated vasculitis. However, some patients suffer from refractoriness and intolerance to cyclophosphamide, creating an unmet need for second-line therapy. Moreover, no guidance has been provided on the choice of immunosuppressant agents for maintenance therapy.

Case presentation: A 55-year-old Asian woman presented with post-prandial vomiting and a persistent high fever for 1 month. She was diagnosed as a double-positive patient after developing rapidly progressive glomerulonephritis, with a creatinine level of 332 μmol/L. She received induction therapy with cyclophosphamide, glucocorticoids, and plasmapheresis soon after diagnosis. However, worsening renal function and severe nausea and vomiting occurred after 3 monthly doses of cyclophosphamide. Four weekly doses of re-induction rituximab at 375 mg/m², followed by maintenance rituximab 500 mg every 6 months, were administered. The patient had a stable creatinine level of 208 μmol/L 17 months after diagnosis.

Conclusion: Rituximab may be a viable alternative as an induction therapy for double-positive patients when first-line cyclophosphamide is not effective or is not tolerated. Moreover, rituximab may be an effective maintenance therapy for double-positive patients. This case study demonstrates not only the efficacy of rituximab in double-positive patients but also reports the first Asian case of the disorder treated successfully with rituximab.