Kidney Week

Abstract: FR-PO0130

Coexisting Myeloperoxidase (MPO)-ANCA Vasculitis and Alport Syndrome

Session Information

• Hereditary Glomerular and Tubulointerstitial Kidney Diseases
  October 23, 2026 | Location: Exhibit Hall A, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Genetic Diseases of the Kidneys

• 1202 Genetic Diseases of the Kidneys: Non-Cystic (Complex and Non-Cystic Monogenic)

Authors

• Tahavvori, Amir, Loma Linda University Medical Center, Loma Linda, California, United States

Amir Tahavvori, MD

• Ebrahimi, Niloufar, Loma Linda University Medical Center, Loma Linda, California, United States

Niloufar Ebrahimi, MD

• Chen Wongworawat, Yan, Loma Linda University Medical Center, Loma Linda, California, United States

Yan Chen Wongworawat

• Abdi Pour, Amir, Loma Linda University Medical Center, Loma Linda, California, United States

Amir Abdi Pour, MD, FASN

Introduction

Alport syndrome (AS) is a hereditary nephropathy caused by pathogenic variants in type IV collagen genes, presenting with glomerular hematuria and progressive kidney disease, often with extrarenal manifestations such as sensorineural hearing loss and ocular abnormalities. Genetic testing has replaced the kidney biopsy for diagnosis. Granulomatosis with polyangitis (GPA) is a type of ANCA-associated vasculitis, mostly characterized by PR3-ANCA positivity.

Case Description

A 27-year-old Hispanic woman with a history of recurrent urinary tract infections, urethral stricture, and persistent microscopic hematuria was referred to the nephrology for kidney stone management. She has been having exertional dyspnea, a nonproductive cough, and recurrent epistaxis. Chest CT scan revealed ground-glass lung nodules, raising concern for a pulmonary-renal syndrome. Labs showed ANA 1:1280, MPO-ANCA 4.1, ESR 62 mm/h, and CRP 20.5 mg/L, and negative PR3. CT of the paranasal sinuses was unremarkable. She was initially treated for the primary GPA diagnosis with methotrexate and later transitioned to rituximab due to liver enzyme elevation. Kidney biopsy showed no evidence of active glomerulonephritis or vasculitis; rather, focal segmental glomerulosclerosis with diffuse glomerular basement membrane thinning, minimal interstitial fibrosis and tubular atrophy. Genetic testing identified a heterozygous pathogenic COL4A4 variant (c.1441G>A; p.Gly481Ser), confirming AS.

Discussion

This case highlights the diagnostic complexity of overlapping hereditary and autoimmune kidney disease. Despite a clinical phenotype consistent with GPA, including lung nodules, epistaxis, and urethral involvement, this patient presented an atypical profile with negative PR3 and positive MPO-ANCA, a pattern observed in about 15% of cases. Notably, her persistent hematuria was not due to vasculitis; instead, it was due to AS. This distinction is crucial, as AS does not account for her systemic manifestations, thereby demonstrating the coexistence of two distinct pathologies. The case further highlights the role of genetic testing in uncovering underlying genetic kidney disease.