ANCA-Associated Vasculitis

Secondary GNmedium

A 50-year-old woman presents with fatigue, arthralgia, and hematuria. Serum creatinine is elevated, MPO-ANCA (p-ANCA) is positive, and kidney biopsy shows pauci-immune necrotizing glomerulonephritis with crescents. Rituximab is not available at her center. Which of the following is an appropriate initial induction regimen?

  1. A.Methotrexate plus folic acid rescue
  2. B.Azathioprine plus oral glucocorticoids
  3. C.Cyclophosphamide and glucocorticoidsCorrect
  4. D.Mycophenolate mofetil monotherapy

Explanation

Crescentic glomerulonephritis is organ-threatening ANCA-associated vasculitis. Induction requires glucocorticoids plus either cyclophosphamide or rituximab; with rituximab unavailable, cyclophosphamide plus a reduced-dose glucocorticoid regimen is appropriate. Methotrexate may be used to induce remission only in selected non-organ-threatening disease with adequate kidney function, so it is inappropriate here. Azathioprine is mainly a maintenance agent, and MMF monotherapy is not adequate for severe renal vasculitis.

Why each option

A.
Methotrexate is not appropriate for induction in severe renal vasculitis and is contraindicated with impaired renal function.
B.
Azathioprine is a maintenance agent, not an induction therapy.
C.
Correct: cyclophosphamide plus glucocorticoids is a standard induction regimen for severe ANCA GN.
D.
Mycophenolate monotherapy is not standard induction for organ-threatening disease (and never as monotherapy).

Reference: KDIGO 2024 ANCA-Associated Vasculitis Guideline, Kidney Int 2024; Walsh M et al. PEXIVAS, NEJM 2020.

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