Pulmonary Pathology Online
Pathology of Eosinophilic granulomatosis with polyangiitis (Churg-Strauss Syndrome)
Eosinophilic granulomatosis with polyangiitis (EGPA), previously known as Churg-Strauss syndrome) is a systemic and pulmonary vasculitis, defined by its association with severe asthma and with hypereosinophilia of the blood and tissues.
First described in 1951 as an allergic and granulomatous angiitis, EGPA is a small-vessel vasculitis.
Mean age at the time of diagnosis is approximately 50 years.
Asthma is the central feature of EGPA and precedes the systemic manifestations in almost all cases, whereas 70% of the patients have maxillary sinusitis, allergic rhinitis, and/or sinus polyposis.
General symptoms are frequent, and associated with pulmonary infiltrates in a large number of the patients. Pulmonary involvement is present in 90% of cases.
Other symptoms include peripheral neuropathy, usually mononeuritis multiplex ; skin involvement (purpura & nodules), arthritis/arthralgia and gastrointestinal tract symptoms. Glomerulonephritis is uncommon.
Cardiac involvement is common and 50% of patients have myocardial or pericardial lesions and represents the primary cause of mortality.
On presentation, Churg-Strauss syndrome needs to be differentiated from other eosinophilic pneumonias, idiopathic hypereosinophilic syndrome, and Wegener's granulomatosis and microscopic polyangiitis.
Hypereosinophilia is the main biological feature of CSS, whereas antineutrophil cytoplasm antibodies (ANCA), especially anti-myeloperoxidase (MPO), are found in one third to one half of the patients.
Triggering factors, such as vaccination, desensitization, or exposure to leukotriene-receptor antagonists, have been suspected as contributing to the development of CSS, but its etiology has not yet been fully elucidated.
The most frequent pulmonary signs of EGPA on computed tomography are ground glass areas or parenchymal consolidation in dispersed bands or with a predominantly subpleural distribution that expresses eosinophilic interstitial and alveolar infiltration.
The complete syndrome, as described by Churg and Strauss, also requires biopsy evidence of extra-vascular granulomas.
The development of symptoms tends to follow a pattern, beginning with allergic rhinitis and asthma, followed after a variable period, sometimes years, by blood and tissue eosinophilia.
Finally, evidence of systemic vasculitis develops.
Pulmonary infiltrates vary from diffuse transient shadowing to multiple nodules, corresponding to dense infiltration of the lung by eosinophils, often with central necrosis.
IgE levels may be increased.
Cytology of sputum, lavage fluid or material obtained by percutaneous transthoracic aspiration may be helpful in showing numerous eosinophils and Charcot-Leyden crystals but biopsy is required to confirm the presence of vasculitis and granulomatous lesions.
Bronchial biopsy is typical of asthma with excessive mucus secretion, desquamation of epithelium and numerous eosinophils.
Transbronchial or transthoracic lung biopsies are usually too small to reveal granulomas and the appearances in heavily infiltrated areas of the lung are identical to those in eosinophilic pneumonia.
Eosinophils are present in large numbers in alveolar spaces and in the interstitium with widening of alveolar septa.
Organization of intra-alveolar exudates may be present.
Many of the eosinophils are degenerate with areas of necrosis containing eosinophilic debris.
Vasculitis is difficult to identify as fibrinoid necrosis and capillaritis are unusual.
More commonly, small muscular arteries and veins are surrounded by inflammatory cells, mainly eosinophils, with infiltration of the wall and mural fibrosis.
Granulomas are infrequent and similar to the palisading granulomas of Wegener's Granulomatosis ; consisting of irregular clusters of histiocytes and giant cells surrounding densely eosinophilic granular necrotic material.
Cases meeting all criteria for the Churg-Strauss syndrome are rare.
Some authors emphasize the clinical criteria and extend the term to a larger group of patients, who show evidence of systemic vasculitis associated with eosinophilia and asthma.
The concept of "limited" forms of the disease has been proposed for those cases where neither the clinical nor pathological criteria are met and the process may be confined to a single organ.
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