Granulomatosis with Polyangiitis
A life-threatening systemic vasculitis driven by PR3-ANCA, causing necrotizing granulomas in the upper/lower respiratory tract and rapidly progressive glomerulonephritis.
Emergency Management: Diffuse Alveolar Hemorrhage (DAH) requiring emergent intubation, mechanical ventilation, high-dose IV pulse steroids, and potential plasmapheresis.
Granulomatosis with polyangiitis (GPA) is a rare, life-threatening systemic autoimmune disease characterized by necrotizing granulomatous inflammation and small-to-medium vessel vasculitis. It predominantly affects the upper and lower respiratory tracts and the kidneys. The core pathology involves antineutrophil cytoplasmic antibodies (ANCA) that target proteinase 3 (PR3), leading to endothelial damage.
Detailed Overview
GPA is part of the ANCA-associated vasculitides, along with microscopic polyangiitis and eosinophilic granulomatosis with polyangiitis. Its clinical significance lies in its propensity for rapid multi-organ destruction; without treatment, the 1-year mortality rate approaches 80%, primarily due to rapidly progressive glomerulonephritis or massive alveolar hemorrhage. Pathogenesis is driven by PR3-ANCA, which primes neutrophils to undergo premature degranulation and release reactive oxygen species upon binding to endothelial surfaces. Early recognition is vital because modern immunosuppressive therapy has transformed this once-fatal disease into a chronic relapsing condition with a >80% 5-year survival rate.
Epidemiology & Demographics
Incidence: 10-20 cases per 1 million person-years. Prevalence: 150-250 per 1 million. Age distribution: Peak onset between 40 and 65 years. Gender ratio: Equal (1:1). Geographic patterns: Higher prevalence in Northern Europe and populations of European descent; rare in African and Asian populations.
Etiological Mechanism
The exact etiology is unknown, but it is considered an autoimmune reaction triggered by environmental factors (e.g., Staphylococcus aureus infection, silica exposure) in genetically susceptible individuals (e.g., HLA-DPB1*04:01 allele).
Primary Causes
Primary: Idiopathic autoimmune response with PR3-ANCA production
Secondary: Putative triggers include chronic nasal carriage of S. aureus and exposure to silica dust
The mechanism begins when a priming event (like a viral/bacterial infection) causes pro-inflammatory cytokines (TNF-alpha, IL-1) to upregulate the expression of proteinase 3 (PR3) and myeloperoxidase (MPO) on the surface of neutrophils. Circulating PR3-ANCA binds to these antigens, excessively activating the neutrophils. These activated neutrophils adhere to the vascular endothelium of small-to-medium vessels, undergo degranulation, release toxic oxygen radicals, and extrude neutrophil extracellular traps (NETs). This direct endothelial injury causes necrotizing vasculitis and the formation of extravascular granulomas, leading to tissue ischemia, necrosis (e.g., saddle nose deformity, cavitary lung lesions), and crescentic glomerulonephritis.
Diagnostic Criteria & Guidelines
Diagnosis requires clinical signs of vasculitis plus biopsy evidence (necrotizing granulomatous inflammation/vasculitis) and/or positive PR3-ANCA serology. The 2022 ACR/EULAR classification criteria assign points for: bloody nasal discharge/crusting (+3), cartilaginous involvement (+2), conductive hearing loss (+1), c-ANCA/PR3-ANCA positive (+5), pulmonary nodules/cavitation (+2), granuloma on biopsy (+2). A score of >= 5 is diagnostic.
Remission induction for severe disease: Rituximab 375 mg/m2 IV weekly for 4 weeks (OR Cyclophosphamide 15 mg/kg IV every 2-3 weeks) PLUS high-dose Glucocorticoids (e.g., Methylprednisolone 500-1000 mg IV daily for 3 days, followed by Prednisone 1 mg/kg/day PO taper).
Second-Line & Adjunctive Therapy
For refractory disease or specific contraindications: Mycophenolate mofetil 1000 mg PO BID. Plasma exchange may be considered in concurrent Anti-GBM disease or severe diffuse alveolar hemorrhage, though the PEXIVAS trial reduced its general use.
Surgical & Procedural Management
Endoscopic dilation or surgical reconstruction for subglottic stenosis; kidney transplantation for ESRD (after 6 months of remission).
Patient Counseling & Advice
Patients must be educated on the chronic, relapsing nature of GPA. Discuss the importance of medication adherence, particularly regarding glucocorticoids and Rituximab. Warn about the signs of relapse (e.g., returning sinus symptoms, joint pain, hematuria) and the risks of immunosuppression, including opportunistic infections.
Follow-Up & Monitoring Schedule
Monthly clinic visits during induction. Routine monitoring includes Urinalysis, Serum Creatinine, CBC, and CRP every 1-3 months. Serial ANCA titers can be checked but should not solely dictate treatment decisions without clinical signs of relapse.
Preventive Strategies
No primary prevention exists. Secondary prevention of relapse relies on maintenance therapy (e.g., Rituximab 500 mg IV every 6 months or Azathioprine 2 mg/kg/day) for 18-24 months or longer.
With treatment, >80% achieve remission, but up to 50% relapse within 5 years. 5-year survival is 75-85%. Mortality is often due to treatment-related complications (infections) or cardiovascular disease.