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rheum.mpa.core.v1PRODUCTION
rheum.mpa.core.v1

Microscopic polyangiitis (MPA)

rheumatologyacutechronicadult
Hard-required inputs
0 / 12
Care setting:

Encounter flow

12/12 authored

Canonical 12-phase frame with authored status for this dossier.

Current phase

Frame

Detailed

Adult with suspected ANCA-associated small-vessel vasculitis. Define MPA: necrotizing pauci-immune small-vessel vasculitis WITHOUT granulomas; NO destructive ENT/granulomatous masses (key vs GPA). New-onset vs relapse vs ILD-predominant

Inputs
1
Actions
0
Advance rule
Set
Advance when

AAV scope confirmed; MPA phenotype suspected

Patient inputs (12)

Double-positive (ANCA + anti-GBM) changes prognosis and mandates plasma exchange; must be excluded

DAH (ground-glass), fibrotic UIP-like MPA-ILD (often anti-MPO, may precede vasculitis, worse prognosis)

Older age + frailty affects cyclophosphamide vs rituximab choice and reduced-dose PEXIVAS glucocorticoid taper

Hydralazine, levamisole-adulterated cocaine, propylthiouracil, minocycline cause drug-induced ANCA — withdraw offending agent

Prior CYC/RTX exposure, HBV/HCV/TB status, active infection — alters induction agent and prophylaxis

Anti-MPO (p-ANCA) typical of MPA; ELISA confirmation; PR3 favors GPA; double-positive screens anti-GBM differential

PR3 (c-ANCA) pivots toward GPA; informs relapse risk and rituximab maintenance duration

Cr trend defines RPGN severity and dialysis-dependence; drives PEXIVAS plasma-exchange decision and CYC dose

Dysmorphic RBCs / RBC casts = active glomerular inflammation; defines renal vasculitis activity

Anemia from DAH/chronic disease; baseline before cyclophosphamide cytopenia surveillance

Inflammatory burden; supports activity and tracks treatment response and relapse

Hypoxia from alveolar hemorrhage = life-threatening; drives ICU disposition and plasma exchange

* = hard-required. Engine cannot meaningfully run until these are filled.

Severity triggers (6)

6 need judgement
  • informationallife_threateningdiffuse_alveolar_hemorrhage
    Hypoxia + hemoptysis + diffuse infiltrates + falling Hb (pulmonary capillaritis)
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationallife_threateningdialysis_dependent_rpgn
    Rapidly progressive crescentic GN with dialysis-dependent AKI
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationallife_threateningdouble_positive_anti_gbm
    ANCA-positive AND anti-GBM-positive (double-positive disease)
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationallife_threateningrapidly_progressive_ild_respiratory_failure
    Rapidly progressive fibrotic MPA-ILD with hypoxemic respiratory failure
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationalseveremononeuritis_multiplex_motor
    Asymmetric motor/sensory deficit — vasculitic mononeuritis multiplex
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationalmoderatedrug_induced_anca_offender
    Hydralazine / levamisole-adulterated cocaine / propylthiouracil / minocycline exposure with ANCA positivity
    Trigger could not be auto-evaluated — needs clinician judgement.

Workflow calculators

Run this disease's risk and dosing calculators inline.

RISK_STRATIFICATIONoptionalDrives severity classification
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Recommended regimen

MPA — severity triage → induction (GC PEXIVAS taper + RTX/CYC ± PEX ± avacopan) → prophylaxis → maintenance → ILD → relapse/ESKD (2021 ACR/VF + KDIGO 2024)
axis: mpa_severity_induction_maintenancestep 1 - Severity triage — organ/life-threatening vs non-severe
Selected step "Severity triage — organ/life-threatening vs non-severe" — Confirmed / highly suspected MPA; classify by organ involvement (RPGN, DAH, mononeuritis multiplex = severe)
  • renal biopsy
    first line
    diagnostic_procedure
    procedure
    triggers: rising_creatinine, active_urine_sediment, rpgn
    2021 ACR/VF — pauci-immune necrotizing crescentic GN; distinguish from anti-GBM linear IgG and immune-complex GN; % normal glomeruli prognosticates renal recovery
  • plasma exchange (selective)
    add on
    extracorporeal_therapy
    extracorporeal • 7 exchanges over 14 days (typical)
    triggers: dialysis_dependent_RPGN, severe_AKI_from_GN, diffuse_alveolar_hemorrhage, concomitant_anti_GBM
    PEXIVAS — NOT routine; selective for dialysis-dependent / severe AKI from GN or DAH; standard of care if concomitant anti-GBM

outpatient playbook — drug actions (3)

  1. 1. rituximab maintenance
    500 mg IV q6 months (prolonged) • IV • q6 months
    trigger: Remission maintenance
    MAINRITSAN
  2. 2. azathioprine alternative
    2 mg/kg/day (after TPMT) • PO • daily
    trigger: Rituximab unavailable / post-CYC maintenance
    CYCAZAREM / IMPROVE
  3. 3. low-dose prednisone (tapering/off)
    ≤5 mg/day, taper toward discontinuation • PO • daily
    trigger: Maintenance
    PEXIVAS reduced-dose / minimise cumulative GC

Auto-drafted A&P note

outpatient

Subjective

- Possible entry pathways: Positive MPO-ANCA + rising creatinine / active urine sediment; Pulmonary-renal syndrome — hemoptysis / hypoxia + RPGN; Dysmorphic RBCs / RBC casts + rising Cr (pauci-immune RPGN).

Objective

- No vitals, labs, or imaging entered for this encounter.

Assessment

**Microscopic polyangiitis (MPA)** (rheum.mpa.core.v1).
Phenotype framing: Pivot MPA vs GPA (PR3/c-ANCA, granulomatous destructive ENT, more relapse) vs EGPA (asthma + eosinophilia); exclude anti-GBM disease (double-positive), immune-complex GN (IgA vasculitis, cryoglobulinemia, lupus nephritis, post-infectious), drug-induced ANCA (hydralazine, levamisole-cocaine, PTU, minocycline), infective endocarditis mimic, and idiopathic pulmonary fibrosis when ILD precedes vasculitis
Scope: Adult with suspected ANCA-associated small-vessel vasculitis. Define MPA: necrotizing pauci-immune small-vessel vasculitis WITHOUT granulomas; NO destructive ENT/granulomatous masses (key vs GPA). New-onset vs relapse vs ILD-predominant

No severity triggers fired against current inputs.

Plan

Regimen axis: **MPA — severity triage → induction (GC PEXIVAS taper + RTX/CYC ± PEX ± avacopan) → prophylaxis → maintenance → ILD → relapse/ESKD (2021 ACR/VF + KDIGO 2024)** — step "Severity triage — organ/life-threatening vs non-severe".
1. renal biopsy procedure (diagnostic_procedure, first line) — 2021 ACR/VF — pauci-immune necrotizing crescentic GN; distinguish from anti-GBM linear IgG and immune-complex GN; % normal glomeruli prognosticates renal recovery
2. plasma exchange (selective) extracorporeal 7 exchanges over 14 days (typical) (extracorporeal_therapy, add on) — PEXIVAS — NOT routine; selective for dialysis-dependent / severe AKI from GN or DAH; standard of care if concomitant anti-GBM

Setting playbook (outpatient) — Induce/maintain remission in non-severe limited MPA, monitor renal function and ANCA, prevent and detect relapse, manage long-term risk
3. rituximab maintenance 500 mg IV q6 months (prolonged) IV q6 months — Remission maintenance (MAINRITSAN)
4. azathioprine alternative 2 mg/kg/day (after TPMT) PO daily — Rituximab unavailable / post-CYC maintenance (CYCAZAREM / IMPROVE)
5. low-dose prednisone (tapering/off) ≤5 mg/day, taper toward discontinuation PO daily — Maintenance (PEXIVAS reduced-dose / minimise cumulative GC)

Non-pharmacologic actions:
- Relapse surveillance education + return precautions (2021 ACR/VF)
- CV risk modification, malignancy surveillance (CYC bladder/heme) (2021 ACR/VF)
- Inactivated vaccination; avoid live vaccines on immunosuppression (2021 ACR/VF)
- ESKD/transplant pathway counselling if applicable (KDIGO 2024 ANCA GN)

AVOID / contraindication checks:
- Cyclophosphamide gonadotoxic — fertility counsel + GnRH/cryopreservation (2021 ACR/VF)
- MESNA uroprotection with IV cyclophosphamide (2021 ACR/VF)
- No live vaccines on immunosuppression (2021 ACR/VF)
- Rituximab HBV screen + antiviral prophylaxis pre dose (2021 ACR/VF)
- Hold rituximab/cyclophosphamide with active serious infection (2021 ACR/VF)
- PJP prophylaxis during induction immunosuppression (2021 ACR/VF)
- Azathioprine TPMT test pre prescription (2021 ACR/VF)
- Avacopan hepatotoxicity — LFT monitoring (ADVOCATE Jayne 2021)
- Methotrexate avoid in significant renal impairment (2021 ACR/VF)

Monitoring

Regimen monitoring:
- creatinine + urinalysis for renal response (KDIGO 2024 ANCA GN)
- ANCA trend — rising titer + clinical features suggests relapse, not titer alone (2021 ACR/VF)
- CBC weekly during cyclophosphamide (cytopenia nadir) (2021 ACR/VF)
- CD19 B-cells + serum IgG before rituximab redosing (2021 ACR/VF)
- infection surveillance on immunosuppression (2021 ACR/VF)
- PFTs + HRCT if MPA-ILD (INBUILD Flaherty 2019)
- LFTs on avacopan (ADVOCATE Jayne 2021)
- glucocorticoid taper adherence to PEXIVAS reduced-dose schedule (PEXIVAS Walsh 2020)

Setting (outpatient) monitoring:
- Creatinine + UA q1-3 months then per stability (KDIGO 2024 ANCA GN)
- ANCA trend with clinical correlation (2021 ACR/VF)
- CBC + LFT for azathioprine (2021 ACR/VF)
- PFTs/HRCT interval for MPA-ILD (INBUILD Flaherty 2019)

Follow-up plan: Prolonged maintenance (rituximab or azathioprine) with relapse surveillance; ESKD pathway and kidney transplant timing (defer until sustained remission); MPA-ILD progression monitoring ± antifibrotic; long-term CV risk modification, infection prophylaxis, malignancy surveillance (CYC bladder/hematologic); vaccination (avoid live vaccines on immunosuppression); fertility/family planning
- Close-out criterion: maintenance + long-term risk plan documented

Monitoring phase: Cr + UA for renal response; ANCA trend (rising titer + clinical features suggests relapse, not titer alone); CBC weekly during CYC (cytopenia nadir); CD19 B-cells + IgG before rituximab redosing; infection surveillance on immunosuppression; PFTs + HRCT if MPA-ILD; glucocorticoid taper adherence to PEXIVAS schedule

Disposition

Current setting: outpatient — Induce/maintain remission in non-severe limited MPA, monitor renal function and ANCA, prevent and detect relapse, manage long-term risk

Disposition criteria:
- Continue outpatient unless organ-threatening relapse (2021 ACR/VF)

Escalation triggers (move to higher acuity):
- New active sediment / rising Cr → urgent renal workup + re-induction (KDIGO 2024 ANCA GN)
- Hemoptysis / hypoxia → ED for DAH (2021 ACR/VF)
- New mononeuritis multiplex / major relapse → expedited inpatient re-induction (2021 ACR/VF)

Earlier-Return Triggers

Return-precaution thresholds (watch for):
- [LIFE_THREATENING] Hypoxia + hemoptysis + diffuse infiltrates + falling Hb (pulmonary capillaritis)
- [LIFE_THREATENING] Rapidly progressive crescentic GN with dialysis-dependent AKI
- [LIFE_THREATENING] ANCA-positive AND anti-GBM-positive (double-positive disease)

Citations

- 2021 ACR/VF Vasculitis Guideline (ANCA-associated) + KDIGO 2024 ANCA GN + 2022 ACR/EULAR classification + PEXIVAS/ADVOCATE/RAVE [PMID:34235894](https://pubmed.ncbi.nlm.nih.gov/34235894/)
- Cited evidence (PMID 32053298) [PMID:32053298](https://pubmed.ncbi.nlm.nih.gov/32053298/)
- Cited evidence (PMID 33596356) [PMID:33596356](https://pubmed.ncbi.nlm.nih.gov/33596356/)
- Cited evidence (PMID 20647198) [PMID:20647198](https://pubmed.ncbi.nlm.nih.gov/20647198/)
- Cited evidence (PMID 35110332) [PMID:35110332](https://pubmed.ncbi.nlm.nih.gov/35110332/)

Last reconciled with current guidelines: 2026-05-22.
References
  • 2021 ACR/VF Vasculitis Guideline (ANCA-associated) + KDIGO 2024 ANCA GN + 2022 ACR/EULAR classification + PEXIVAS/ADVOCATE/RAVE — PMID:34235894
  • Cited evidence (PMID 32053298) — PMID:32053298
  • Cited evidence (PMID 33596356) — PMID:33596356
  • Cited evidence (PMID 20647198) — PMID:20647198
  • Cited evidence (PMID 35110332) — PMID:35110332