What is the recommended treatment for pauci‑immune perinuclear ANCA‑associated rapidly progressive glomerulonephritis?

Treatment of Pauci-Immune pANCA-Associated RPGN

For pauci-immune pANCA (MPO-ANCA) associated rapidly progressive glomerulonephritis, initiate immediate treatment with glucocorticoids combined with either rituximab or cyclophosphamide—do not delay for biopsy confirmation if clinical presentation and positive serology are consistent with ANCA-associated vasculitis. 1

Immediate Induction Therapy

First-Line Regimen

The cornerstone of treatment is combination therapy with:

• Glucocorticoids PLUS either rituximab OR cyclophosphamide 2, 1

Choosing Between Rituximab vs Cyclophosphamide

Rituximab is preferred for:

• Relapsing disease (superior efficacy demonstrated) 2
• PR3-ANCA positive patients (though your patient has pANCA/MPO-ANCA)
• Patients of childbearing age
• Those wishing to avoid cyclophosphamide toxicity

Cyclophosphamide is preferred for:

• Severe renal disease with serum creatinine >4 mg/dL (>354 μmol/L) 1
• Rapidly declining GFR or dialysis-dependent patients
• Limited data support rituximab alone in this severe presentation

Critical caveat: In patients with markedly reduced or rapidly declining GFR (SCr >4 mg/dL), there are limited data supporting rituximab monotherapy with glucocorticoids. Consider either cyclophosphamide with glucocorticoids OR a combination of rituximab with 2 pulses of intravenous cyclophosphamide 1.

Specific Dosing Protocols

Glucocorticoid Regimen

Start with prednisolone 50-75 mg/day (based on body weight):

• <50 kg: 50 mg/day
• 50-75 kg: 60 mg/day

• 75 kg: 75 mg/day

Taper schedule (PEXIVAS protocol) 1:

• Week 1: Starting dose
• Week 2: Reduce to 25-40 mg (weight-based)
• Weeks 3-4: 20-30 mg
• Progressive taper to reach 5 mg/day by 4-5 months 2

Immunosuppressive Agent Dosing

Rituximab: 375 mg/m² weekly × 4 weeks 1

Cyclophosphamide options:

• Oral: 2 mg/kg/day for 3 months (reduce for age: 1.5 mg/kg if >60 years, 1.0 mg/kg if >70 years; reduce by 0.5 mg/kg/day if GFR <30 mL/min/1.73m²) 1
• Intravenous: 15 mg/kg at weeks 0,2,4,7,10,13 (reduce for age: 12.5 mg/kg if >60 years, 10 mg/kg if >70 years; reduce by 2.5 mg/kg if GFR <30 mL/min/1.73m²) 1

Combined approach for severe disease: Rituximab 375 mg/m² weekly × 4 weeks PLUS cyclophosphamide 15 mg/kg at weeks 0 and 2 1

Adjunctive Therapies

Plasma Exchange

Consider plasma exchange for:

• Serum creatinine >3.4 mg/dL (>300 μmol/L) 1
• Dialysis-dependent patients
• Rapidly increasing creatinine
• Diffuse alveolar hemorrhage with hypoxemia 1

Important note: The 2024 KDIGO guidelines indicate plasma exchange may be considered but is not routinely recommended for all severe cases, reflecting evolving evidence from the PEXIVAS trial 1. The EULAR 2024 guidelines similarly state plasma exchange may be considered for SCr >300 μmol/L but do not recommend routine use for alveolar hemorrhage 2.

Avacopan

Avacopan (30 mg twice daily) may be used as a glucocorticoid-sparing agent in combination with rituximab or cyclophosphamide, particularly beneficial for:

• Patients at high risk of glucocorticoid toxicity
• Those with lower GFR who may benefit from greater GFR recovery 2, 1

Maintenance Therapy

After achieving remission (typically 3-6 months):

First-line maintenance: Rituximab (preferred after either rituximab or cyclophosphamide induction) 2, 1

• MAINRITSAN protocol: 500 mg × 2 at remission, then 500 mg at months 6,12,18
• OR RITAZAREM protocol: 1000 mg after induction, then at months 4,8,12,16

Alternative maintenance options:

• Azathioprine 1.5-2 mg/kg/day with low-dose glucocorticoids 1
• Mycophenolate mofetil 2000 mg/day (divided doses) 1
• Methotrexate (only if GFR >60 mL/min/1.73m²) 1

Duration: Continue maintenance therapy for 24-48 months for new-onset disease; longer duration (up to 4 years) for relapsing patients or those at high relapse risk 2, 1

Critical Management Principles

Do Not Delay Treatment

In rapidly deteriorating patients with clinical presentation compatible with ANCA vasculitis and positive pANCA/MPO-ANCA serology, start treatment immediately—do not wait for kidney biopsy results 1. Biopsy can be performed soon after starting treatment to confirm diagnosis.

Multidisciplinary Care

Patients should be managed at centers with expertise in ANCA-associated vasculitis, given the rarity, heterogeneity, and life-threatening nature of the disease 2, 1.

Monitoring for Relapse

• Persistence of ANCA positivity, rising ANCA levels, or conversion from negative to positive predicts future relapse 1
• Return of hematuria after initial resolution may indicate kidney relapse 1
• pANCA/MPO-ANCA patients generally have lower relapse rates than PR3-ANCA patients

Prophylaxis

Implement prophylaxis against treatment-related complications:

• Pneumocystis jirovecii pneumonia prophylaxis (trimethoprim-sulfamethoxazole)
• Bone protection (calcium, vitamin D, bisphosphonates if indicated)
• Infection surveillance (major cause of early mortality) 3

Common Pitfalls to Avoid

1. Delaying treatment while awaiting biopsy in a rapidly deteriorating patient with compatible clinical picture and positive serology
2. Using rituximab monotherapy in severe renal disease (SCr >4 mg/dL) without considering cyclophosphamide or combination therapy
3. Inadequate glucocorticoid tapering—follow structured protocols to balance efficacy and toxicity
4. Premature discontinuation of maintenance therapy—minimum 24 months, longer for relapsing disease
5. Overlooking infection risk—the leading cause of death in the first year is infection, not active vasculitis 3