Eosinophilic granulomatosis with polyangiitis (Churg-Strauss, EGPA) is a systemic small-to-medium-sized vasculitis associated with asthma and eosinophilia. Histologically EGPA presents tissue eosinophilia, necrotizing vasculitis, and granulomatous inflammation with eosinophil tissue infiltration. EGPA commonly involves the upper airway and lung parenchyma, peripheral neuropathy, cardiac disorders, and skin lesions. The anti-neutrophil cytoplasmic antibodies (ANCA) are positive in 40% of cases, especially in those patients with clinical signs of vasculitis. The pathogenesis of EGPA is multifactorial. The disease can be triggered by exposure to a variety of allergens and drugs, but a genetic background has also been described, particularly an association with HLA-DRB4. Th2 response is of special importance in the upregulation of different interleukins such as IL-4, IL-13, and IL-5. Th1 and Th17 responses are also of significance. Activated eosinophils have a prolonged survival and probably cause tissue damage by releasing eosinophil granule proteins, while their tissue recruitment can be regulated by chemokines such as eotaxin-3 and CCL17. Humoral immunity is also abnormally regulated, as demonstrated by excessive responses of IgG4
and IgE. EGPA has a good respond to glucocorticoids, although the combination of glucocorticoids and immunosuppressants (e.g., cyclophosphamide, azathioprine) is needed in most of cases. Newer treatment options include anti-IL-5 antibodies (mepolizumab), whose efficacy has been described in clinical trials, and anti-CD-20, a B cell-depleting agent (rituximab), reported in several case series.
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