What is Wegener's granulomatosis (granulomatosis with polyangiitis)?

What is Wegener's Granulomatosis (Granulomatosis with Polyangiitis)?

Wegener's granulomatosis, now officially renamed granulomatosis with polyangiitis (GPA), is a systemic necrotizing vasculitis affecting small- to medium-sized blood vessels, characterized by the classic triad of necrotizing granulomas of the upper and/or lower respiratory tract, necrotizing vasculitis of arteries and veins (especially in the lungs), and pauci-immune glomerulonephritis 1.

Disease Definition and Nomenclature

The condition was first described by German pathologist Friedrich Wegener in 1936 2. In 2012, the nomenclature was officially changed from "Wegener's granulomatosis" to "granulomatosis with polyangiitis" (GPA) 3. This is one of the ANCA-associated vasculitides (AAV), a group that also includes microscopic polyangiitis and eosinophilic granulomatosis with polyangiitis 4, 5.

Clinical Manifestations

Upper Respiratory Tract (70-100% of cases)

The upper respiratory tract is involved in the vast majority of cases and often represents the first clinical manifestation 6:

• Nasal symptoms: Persistent bleeding, crusting, obstruction, bloody nasal discharge
• Sinus involvement: Chronic sinusitis with inflammation
• Destructive lesions: Septal perforation can develop
• Otologic disease: Occurs in approximately 35% of cases (range 19-61%)

The classic acronym ELK describes involvement of the Ear, nose, and throat (ENT); Lungs; and Kidneys 6.

Lower Respiratory Tract (>90% of cases)

Pulmonary involvement is nearly universal 1:

• Cough and hemoptysis occur in >95% of patients
• Chest imaging shows unilateral or bilateral infiltrates, nodules, and cavitation
• Diffuse alveolar infiltrates may indicate life-threatening alveolar hemorrhage
• Tracheobronchial stenosis occurs in 15% of patients
• Subglottic stenosis develops in 5-23% of treated patients, presenting insidiously with persistent cough, wheezing, and dyspnea that may initially be misdiagnosed as asthma

Renal Involvement

• Rapidly progressive pauci-immune glomerulonephritis is characteristic 5
• Necrotizing crescentic glomerulonephritis without significant immune complex deposition
• Can progress to dialysis-dependence if untreated

Systemic Features

The clinical presentation varies from subacute nonspecific respiratory illness to rapidly progressive respiratory insufficiency with multisystem involvement 1.

Diagnostic Approach

Serologic Testing

Anti-neutrophil cytoplasmic antibodies (ANCA) are the serologic hallmark 3:

• PR3-directed c-ANCA is present in 80-90% of systemic GPA cases
• In localized disease (limited to sinonasal tract), ANCA can be negative in up to 50% of cases, making diagnosis challenging
• ANCA positivity is not essential for clinical diagnosis, but when present, is highly specific 7, 8

Histopathology

The diagnosis is established by the combination of 3:

• Clinical features of systemic vasculitis
• Positive ANCA serology (when present)
• Necrotizing vasculitis on biopsy
• Granulomatous inflammation on biopsy

Important caveat: Nasal biopsies often lack sufficient specific features to confirm the diagnosis, and biopsies from other involved organs may be required 3.

Classification Criteria

The 2022 ACR/EULAR classification criteria for GPA include a points-based system (≥5 points needed after excluding mimics) 9:

• Bloody nasal discharge, crusting, or congestion (+3)
• Cartilaginous involvement (+2)
• c-ANCA or anti-PR3 ANCA positivity (+5)
• Pulmonary nodules, mass, or cavitation (+2)
• Granuloma or giant cells on biopsy (+2)
• Pauci-immune glomerulonephritis (+1)
• p-ANCA or anti-MPO ANCA positivity (-1)
• Eosinophil count ≥1×10⁹/L (-4)

This system achieved 93% sensitivity and 94% specificity in validation 9.

Epidemiology

• Prevalence: 24-157 cases per million in European populations, with highest rates in Sweden and the UK 4
• Age: Can occur at any age (range 8-99 years), but typically affects adults 6
• Race: Predominantly affects Caucasians, though can occur in all racial groups 6
• Sex: Both sexes affected equally 6

Prognosis and Natural History

Without treatment, GPA had a dismal prognosis with median survival of approximately 5 months 4. Modern immunosuppressive therapy has dramatically reversed this outcome:

• Complete remission is achieved in >90% of patients with standard therapy 1
• Median time to remission: 12 months 1
• Relapse rate: 50-70% of patients experience relapses, making GPA the AAV with the highest relapse frequency 5
• 10-year survival: 40% when kidneys are involved, 60-70% without kidney involvement 6

Treatment Overview

Remission Induction

Initial treatment combines systemic corticosteroids with either cyclophosphamide or rituximab 5:

• Cyclophosphamide and corticosteroids are recommended for initial treatment (1A recommendation) 5
• Rituximab and corticosteroids are recommended as an alternative, particularly in patients without severe disease or when cyclophosphamide is contraindicated (1B recommendation) 5

Maintenance Therapy

Maintenance therapy is essential and should be continued for at least 18 months in patients who achieve complete remission 5:

• Azathioprine 1-2 mg/kg/day orally is the recommended first-line maintenance agent (1B recommendation) 5
• Mycophenolate mofetil up to 1 g twice daily can be used in patients allergic to or intolerant of azathioprine (2C recommendation) 5
• Maintenance therapy prevents the high relapse rate seen when treatment is stopped shortly after induction 5

Special Considerations

• Airway stenosis may require bronchoscopic interventions including dilation, YAG laser treatment, or stent placement 1
• Plasmapheresis is recommended in conjunction with corticosteroids and cyclophosphamide for pulmonary hemorrhage requiring mechanical ventilation, despite uncertain independent benefit, due to the high mortality risk 5
• Trimethoprim-sulfamethoxazole is suggested as adjunct maintenance therapy in patients with upper respiratory tract disease (2B recommendation) 5

Key Clinical Pitfalls

1. Misdiagnosis as asthma: Subglottic stenosis presents insidiously with cough, wheezing, and dyspnea; abnormal flow-volume loops should prompt further investigation 1

2. Negative ANCA in localized disease: Up to 50% of patients with disease limited to the sinonasal tract may be ANCA-negative, requiring high clinical suspicion 3

3. Inadequate biopsy specimens: Nasal biopsies frequently lack diagnostic features; consider biopsies from other involved organs 3

4. Prolonged treatment toxicity: The severity and frequency of treatment side effects are often linked to the prolonged treatment course required to prevent relapses 7