Pulmonary Pathology Online
Pathology of Wegener's Granulomatosis (Granulomatosis with Polyangiitis)
with Polyangiitis) is a necrotizing, granulomatous vasculitis that has a
clinical predilection to involve the upper airways, lungs, and kidneys.
Although the first case was reported by Klinger in 1931, Friedrich Wegener in 1936 characterized the unique clinical and pathological features of this disease that subsequently came to bear his name.
Vascular inflammation and occlusion leading to tissue ischemia is a hallmark of WG.
Although strong evidence indicates that such blood vessel damage is immunologically mediated, the mechanisms that initiate this process are still largely unknown. To date, there has been no clearly established association with genetic factors, specific infectious agents, or environmental irritants, although speculation has remained that these may play a role in triggering the onset of disease.
Wegener's granulomatosis (WG) starts with granulomatous inflammation of the respiratory tract before it converts into a potentially organ and life threatening systemic vasculitis associated with anti-neutrophil cytoplasmic antibodies (ANCA).
Signs, observed on imaging : The principal pulmonary signs of Wegener's granulomatosis are nodules and masses, sometimes cavitary, and areas of airspace consolidation that may or may not suggest diffuse alveolar hemorrhage.
Main features of classical Wegener's granulomatosis : Necrotizing granulomatous lesions in the upper and lower respiratory tracts, necrotizing vasculitis involving small vessels in the respiratory tract and elsewhere, and focal segmental necrotizing glomerulonephritis with crescent formation.
Organs frequently involved include : Nose ; Lung ; Kidney ; Joints ; Eyes ; Skin ; Ears ; Nervous System ; Trachea/Pharynx ; Heart ; Liver ; Gastrointestinal Tract ; Prostate ; Breast ; Salivary Gland.
Diagnosis of Wegener's granulomatosis : It depends on the combination of clinical and radiological features, positive cANCA serology, and biopsy of the upper respiratory tract, lung or kidney.
Limited Wegener's granulomatosis : Patients with no evidence of renal disease are sometimes regarded as having “limited” WG but this should not be taken to imply that extra-pulmonary lesions are lacking.
Vascular lesions of Wegener's Granulomatosis :
Fibrinoid necrosis of the vessels may be present.
Often the inflammation is less acute with a mixed inflammatory infiltrate in the vessel wall.
Granulomatous vasculitis is very characteristic but not always present.
It takes the form of necrotising palisading granulomas, identical to those seen in extra-vascular lesions, in the walls of vessels.
A segment of the vessel may undergo necrosis with radially oriented histiocytes outlining its course.
There is thrombosis of the lumen with subsequent fibrosis.
Capillaritis can be identified in a number of cases.
Patients may present with intrapulmonary hemorrhage and haemoptysis.
Special stain: Elastic stains help to demonstrate disruption of the elastic laminae in early lesions and to outline the vessel wall in advanced lesions. Loss of integrity of the elastic laminae is a useful point of distinction between true vasculitis and so-called "bystander" vasculitis, occurring in areas of inflammation.
Extra-vascular lesions of Wegener's Granulomatosis :
- Involve both lung parenchyma and mucosal surfaces in the upper respiratory tract and bronchi, sometimes leading to tracheal or bronchial stenosis.
- The earliest mucosal lesions consist of foci of necrotising inflammation and ulceration with occasional multinucleate histiocytic giant cells.
- The fully developed palisading granuloma, the hallmark of WG, takes the form of a stellate focus of necrosis with either fibrinoid material or an aggregate of neutrophils and neutrophil debris, surrounded by a palisade of elongated histiocytes.
- Giant cells are variable in number and are typically "triangular" with a rim of peripheral nuclei.
- Classical sarcoid-like epithelioid and giant cell granulomas may be seen in WG but they are not a typical feature.
- As the granulomas expand and become confluent they produce large, irregular, "geographic" areas of necrosis, typically containing neutrophilic nuclear debris.
- Eosinophils are very variable in WG both in the vascular and extra-vascular lesions and do not form an essential feature of the inflammation.
- Non-specific changes occur around the periphery of the more typical areas and can be misleading in small biopsies. These include localized obstructive pneumonitis with intra-alveolar foamy macrophages, changes resembling bronchiolitis obliterans and organizing pneumonia, and the area of intrapulmonary hemorrhage.
- If the disease has a prolonged course without glomerulonephritis, extravascular lesions predominate and vasculitis may be difficult to identify.
Visit: Pathological Diagnosis of Granulomatous Lung Diseases ; Infectious Granuloma of the Lung ; Non-necrotising Granulomatous Inflammation of the lung ; An approach to Histopathological Examination of Pulmonary Granulomatous Inflammation.
- Occasionally the pulmonary lesions selectively involve the walls of airways (bronchocentric WG) and must be distinguished from bronchocentric granulomatosis.
- At the other end of the spectrum are those patients in whom glomerulonephritis and pulmonary capillaritis dominate the clinical picture and the distinction from microscopic polyangiitis is difficult.
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