Wednesday, November 14, 2012

The Vasculitides: Wegener Granulomatosis (WG)

Although systemic disorders, most of the small-vessel vasculitides seem to have a predilection for the same sites: lungs, kidneys, and skin. Another example of these vascultides -- and probably the most well-known ANCA + vasculitis is Wegener Granulomatosis.

Like Churg-Strauss and Microscopic Polyangiitis, these can attack both the lungs and the kidneys (Goodpasture's syndrome is another condition with pulmonary-renal involvement... but it's not a vasculitis).  Wegener Granulomatosis is actually associated with a triad

1) Upper airway involvement (e.g. sinusitis, tracheobronchial thickening)
2) Lower airway involvment
3) Renal involvment (glomerulonephritis)

(even though the triad is helpful, it's not complete, since WG has been documented to attack just about every system in the body)

Unlike Churg-Strauss and Microscopic Polyangiitis, however, Wegener Granulomatosis has certain radiologic features that are relatively characteristic to it.

The first of these is the characteristic cavitating pulmonary nodules in Wegener Granulomatosis. Although WG can present with a wide variety of nonspecific pulmonary findings, the cavitating nodules are characteristic and "pulmonary nodules or masses" are present in 70% of patients at some point in the disease.

Multiple pulmonary nodules in a first presentation of bx-proven Wegner Granulomatosis.  The groundglass halo is compatible with perinodular capillaritis and alveolar hemorrhage.

Coronal reformat of the patient above

 Another pulmonary manifestation of WG is nonspecific consolidation with groundglass opacities... but WG can only sensibly be entertained after the much more common infectious consolidation has been ruled out.

Upper airway involvement can involve circumferential tracheal thickening...

Example of circumferenctial tracheal thickening in Wegener Granulomatosis.  The differential includes relapsing polychondritis and tracheobronchopathia osteochondroplastica (From ref 2)

The necrotizing vasculitis in WG can also result in severe sinus disease, including destruction of the nasal septum...

On the left is a coronal CT of late-stage Wegener disease with absence of the nasal septum and medial maxillary walls, with reactive changes in the surrounding facial bones.  On the right, an axial T1 images shows similar findings (from ref 3)

Although rare (~3:100,000), WG is one of the more common small vessel vasculitides. Its etiology (inhalational? infectious?) is not clear.

The differential?  Churg-Strauss can appear somewhat similarly, but eosinophilia and a good history of asthma make it a more likely choice. Multiple cavitating masses from metastases (e.g. squamous cell carcinoma) should also be considered. Rhematoid arthritis can present with necrobiotic nodules, but cavitation of the nodules is not common, and history and lab values (RF+, ? ANCA-) can lead away from that choice.
...but as with most vasculitides... biopsy remains the gold standard for diagnosis of WG.

1. "Vasculitis" Ball GV and Bridges SL, ed. Oxford publishers (2002)
2. Martinez F, Chung JH, Digumarthy SR. "Common and Uncommon Manifestations of Wegener Granulomatosis at Chest CT: Radiologic-Pathologic Correlation" RadioGraphics 2012; 32:51–69
3. Valencia MP, Castillo M. "Congenital and Acquired Lesions of the Nasal Septum: A Practical Guide for Differential Diagnosis" January 2008 RadioGraphics, 28, 205-223.