Granulomatosis with Polyangiitis (GPA) is a small-to-medium vessel necrotizing vasculitis. In the 2026 clinical landscape, we prioritize the term GPA over “Wegener’s,” but the radiologic hallmarks remain classic: the multisystem “ELK” distribution (Ears/Nose/Throat, Lungs, and Kidneys).
For the radiologist, GPA is a “chameleon” that can mimic malignancy or infection. Success in reporting lies in recognizing the waxing and waning nature of its nodules and the specific sinonasal destruction patterns.
1. Thoracic Manifestations: The “Cavitating Nodule”
The lung is the most common site of involvement (approx. 90% of cases).
- Nodules and Masses: Typically multiple, bilateral, and random in distribution. They range from a few millimeters to 10 cm.
- Cavitation: Occurs in about 25% of nodules > 2 cm. Look for thick, irregular walls. Unlike a simple abscess, GPA cavities rarely show air-fluid levels unless secondarily infected.
- The “Halo Sign”: A ring of ground-glass opacity (GGO) surrounding a nodule, representing perilesional hemorrhage.
- Diffuse Alveolar Hemorrhage (DAH): Manifests as diffuse, perihilar ground-glass opacities. This is a medical emergency.
2. Head & Neck: The “Saddle Nose” and Beyond
Sinonasal involvement is the earliest feature in up to 90% of patients.
- Sinonasal Destructive Changes: Look for destruction of the nasal septum and turbinates.
- Neo-osteogenesis: A key differentiator! Chronic GPA causes significant reactive bone thickening (sclerosis) of the sinus walls, which is rare in fungal sinusitis or malignancy.
- Orbital Pseudotumor: GPA can cause an extraconal soft tissue mass leading to proptosis and optic nerve compression.
3. The Differential Diagnosis “Gap”
Radiologists often get stuck between GPA and Septic Emboli or Metastases.
| Feature | GPA | Septic Emboli | Metastases |
| Cavitary Wall | Thick and Irregular | Thin/Variable | Thick/Nodular |
| Feeding Vessel | Possible | Common (Feeding Vessel Sign) | Rare |
| Clinical Clue | c-ANCA positive | Fever / IV drug use | Known Primary |
| Sinuses | Often Involved | Usually Normal | Usually Normal |
📋 Copy & Paste Reporting Template
FINDINGS:
Sinonasal:
- Mucosa: [Mucosal thickening / Polypoid changes] identified within the [Maxillary/Ethmoid/Frontal] sinuses.
- Osseous Structures: [Erosion of the nasal septum / Destruction of the turbinates]. Note is made of reactive neo-osteogenesis along the antral walls.
- Orbits: [Normal / Soft tissue mass in the extraconal space].
Chest (Lungs):
- Nodules: Multiple bilateral pulmonary nodules measuring up to [ ] cm. [Number] nodules demonstrate central cavitation with thick, irregular walls.
- Parenchyma: [Patchy ground-glass opacities / Consolidation] noted in the [Location], suggestive of focal hemorrhage vs. pneumonitis.
- Airways: [Normal / Focal subglottic stenosis / Wall thickening].
Associated Findings:
- Pleura: [No pleural effusion / Small bilateral effusions].
- Lymph Nodes: [No significant hilar or mediastinal lymphadenopathy].
IMPRESSION:
- Multisystem findings involving the sinonasal tract and lungs, highly suspicious for Granulomatosis with Polyangiitis (GPA).
- Differential includes septic emboli and metastatic disease, though the associated sinonasal destructive changes and neo-osteogenesis strongly favor a vasculitic process.
- Recommendation: Correlation with c-ANCA (PR3) titers and clinical history of renal dysfunction (hematuria/proteinuria).
