Epidemiology

Etiology

Pathophysiology

• Binding of PR3-ANCA to PR3 activates neutrophils → release of neutrophilic inflammatory mediators, formation of neutrophil extracellular traps, complement activation → damage to endothelial cells of small blood vessels

Clinical features

• ENT involvement: often the first clinical manifestation
  • Chronic rhinitis/sinusitis: nasopharyngeal ulcerations → nasal septum perforation → saddle nose deformity
• Lower respiratory tract: potentially life-threatening
  • Treatment-resistant, pneumonia-like symptoms with cough, dyspnea, hemoptysis
• Renal involvement: potentially life-threatening
  • Pauci-immune glomerulonephritis (Pauci‑immune indicates that there is little evidence of immune complex/antibody deposits.) → rapidly progressive (crescentic) glomerulonephritis (RPGN) with possible pulmonary-renal syndrome
• Usually spares GI
  • Unlike PAN

Diagnostics

• Routine studies
  • Urinalysis: microscopic hematuria, proteinuria
  • Urine sediment: nephritic sediment (dysmorphic RBC and RBC casts)
• Serology: ANCA (positive in ∼ 90% of patients)
  • PR3-ANCA (aka c-ANCA)
• Obtain a chest X-ray or CT chest
  • Supportive findings
    • Multiple bilateral cavitating nodular lesions
    • Pulmonary hemorrhage
• Biopsy
  • Necrosis
  • Vasculitis of small and medium-sized vessels
  • granulomas (mainly in the lungs and upper airways)
  • necrotizing glomerulonephritis

Treatment