J Med Cases

Journal of Medical Cases, ISSN 1923-4155 print, 1923-4163 online, Open Access

Article copyright, the authors; Journal compilation copyright, J Med Cases and Elmer Press Inc

Journal website https://jmc.elmerpub.com

Case Report

Volume 17, Number 11, November 2026, pages 665-669

Myeloperoxidase-Anti-Neutrophil Cytoplasmic Antibody Vasculitis With Isolated Renal Presentation in an Older Female Patient: A Diagnostic and Therapeutic Challenge

↓ **Table 1.** Key Laboratory Findings at Admission
Parameters	Values	Reference ranges
eGFR (CKD-EPI): epidermal glomerular filtration rate (chronic kidney disease epidemiology) collaboration; NT-proBNP: N-terminal proBNP; anti-MPO: anti-myeloperoxidase; p-type ANCA: perinuclear-type anti-neutrophil cytoplasmic antibody; CRP: C-reactive protein; AI: antibody index.
Hemoglobin	9.2 g/dL	11.8–15.0 g/dL
Sodium	132 mmol/L	135–145 mmol/L
Serum creatinine	155 µmol/L	44–71 µmol/L
eGFR (CKD-EPI)	28 mL/min/1.73 m²	> 90 mL/min/1.73 m²
Serum uric acid	74 mg/L	24–66 mg/L
NT-proBNP	588 pg/mL	< 125 pg/mL
CRP	< 4 mg/L	< 10 mg/L
24-h proteinuria	2.5 g/24 h	< 0.14 g/24 h
p-type ANCA (titer)	160 (< 20)	Negative
Anti-MPO	> 8.0 AI	< 1.1 AI
Microalbuminuria	220 mg/L	< 30 mg/L

↓ Table 1. Key Laboratory Findings at Admission

Parameters

Values

Reference ranges

eGFR (CKD-EPI): epidermal glomerular filtration rate (chronic kidney disease epidemiology) collaboration; NT-proBNP: N-terminal proBNP; anti-MPO: anti-myeloperoxidase; p-type ANCA: perinuclear-type anti-neutrophil cytoplasmic antibody; CRP: C-reactive protein; AI: antibody index.

Hemoglobin

9.2 g/dL

11.8–15.0 g/dL

Sodium

132 mmol/L

135–145 mmol/L

Serum creatinine

155 µmol/L

44–71 µmol/L

eGFR (CKD-EPI)

28 mL/min/1.73 m²

> 90 mL/min/1.73 m²

Serum uric acid

74 mg/L

24–66 mg/L

NT-proBNP

588 pg/mL

< 125 pg/mL

CRP

< 4 mg/L

< 10 mg/L

24-h proteinuria

2.5 g/24 h

< 0.14 g/24 h

p-type ANCA (titer)

160 (< 20)

Negative

Anti-MPO

> 8.0 AI

< 1.1 AI

Microalbuminuria

220 mg/L

< 30 mg/L

↓ **Table 2.** Key Laboratory Findings
Parameter	Initial value	Control value	Reference ranges
eGFR (CKD-EPI): epidermal glomerular filtration rate (chronic kidney disease epidemiology) collaboration; anti-MPO-ANCA: anti-myeloperoxidase anti-neutrophil cytoplasmic antibody; CRP: C-reactive protein; AI: antibody index.
Serum creatinine	155 µmol/L	116 µmol/L	44–71 µmol/L
eGFR (CKD-EPI)	28 mL/min/1.73 m²	48 mL/min/1.73 m²	> 60 mL/min/1.73 m²
Hemoglobin	9.2 g/dL	> 12 g/dL	11.8–15.0 g/dL
Sodium	132 mmol/L	137 mmol/L	135–145 mmol/L
24-h proteinuria	2.5 g/24 h	0.6 g/24 h	< 0.14 g/24 h
Anti-MPO-ANCA	> 8.0 AI	Decrease	< 1.1 AI
CRP	< 4 mg/L	Negative	< 10 mg/L

↓ Table 2. Key Laboratory Findings

Parameter

Initial value

Control value

Reference ranges

eGFR (CKD-EPI): epidermal glomerular filtration rate (chronic kidney disease epidemiology) collaboration; anti-MPO-ANCA: anti-myeloperoxidase anti-neutrophil cytoplasmic antibody; CRP: C-reactive protein; AI: antibody index.

Serum creatinine

155 µmol/L

116 µmol/L

44–71 µmol/L

eGFR (CKD-EPI)

28 mL/min/1.73 m²

48 mL/min/1.73 m²

> 60 mL/min/1.73 m²

Hemoglobin

9.2 g/dL

> 12 g/dL

11.8–15.0 g/dL

Sodium

132 mmol/L

137 mmol/L

135–145 mmol/L

24-h proteinuria

2.5 g/24 h

0.6 g/24 h

< 0.14 g/24 h

Anti-MPO-ANCA

> 8.0 AI

Decrease

< 1.1 AI

CRP

< 4 mg/L

Negative

< 10 mg/L

↓ **Table 3.** Summary of Treatments Administered
Treatment	Main modalities	Comments
IV: intravenous; PEXIVAS: plasma exchange and glucocorticoids for treatment of anti-neutrophil cytoplasmic antibody-associated vasculitis.
Corticosteroid therapy	Three bolus doses of methylprednisolone sodium succinate (Solu-Medrol), followed by oral therapy according to PEXIVAS	Planned gradual tapering
Rituximab	375 mg/m² weekly × 4	Diffuse erythematous and pruritic reaction after the first infusion; temporarily discontinued and subsequently re-introduced after allergological assessment using a fractionated protocol, premedication, and a slower infusion rate
Cyclophosphamide	500 mg IV every 2–3 weeks × 6 cycles	Effective temporary replacement
Rituximab (maintenance)	500 mg every 6 months	Successfully re-introduced after allergological assessment and subsequently continued as maintenance therapy
Anti-infective prophylaxis	Atovaquone (Wellvone)	Substitute for trimethoprim–sulfamethoxazole (Bactrim)
Other measures	Vaccination, close monitoring	Good clinical stabilization

↓ Table 3. Summary of Treatments Administered

Treatment

Main modalities

Comments

IV: intravenous; PEXIVAS: plasma exchange and glucocorticoids for treatment of anti-neutrophil cytoplasmic antibody-associated vasculitis.

Corticosteroid therapy

Three bolus doses of methylprednisolone sodium succinate (Solu-Medrol), followed by oral therapy according to PEXIVAS

Planned gradual tapering

Rituximab

375 mg/m² weekly × 4

Diffuse erythematous and pruritic reaction after the first infusion; temporarily discontinued and subsequently re-introduced after allergological assessment using a fractionated protocol, premedication, and a slower infusion rate

Cyclophosphamide

500 mg IV every 2–3 weeks × 6 cycles

Effective temporary replacement

Rituximab (maintenance)

500 mg every 6 months

Successfully re-introduced after allergological assessment and subsequently continued as maintenance therapy

Anti-infective prophylaxis

Atovaquone (Wellvone)

Substitute for trimethoprim–sulfamethoxazole (Bactrim)

Other measures

Vaccination, close monitoring

Good clinical stabilization