Recently, a revised FFS has been proposed an age over 65?years, cardiac symptoms, gastrointestinal involvement, renal insufficiency (serum creatinine >150?mol/L) and absence of ear, nose, and throat manifestations have been pointed out as predictors of 5-year mortality (55). Classically, used therapies in EGPA remission maintenance are azathioprine or methotrexate (56). Although primarily used for GPA, the BVAS, a clinical index of disease activity (57), might be useful to better decide when to stop therapy with CYC and introduce maintenance therapy like azathioprine or methotrexate. Cyclophosphamide toxicity has long been known (58) and, based on our center experience, we recommend not to exceed the dose of 10C15?g of CYC (including both oral and pulse medications). main pathological finding is the eosinophilic organ infiltrations (e.g., lungs, heart, and gastrointestinal system), and the vasculitic phase, characterized by purpura, peripheral neuropathy, and constitutional symptoms. ANCA (especially pANCA anti-myeloperoxidase) are present in 40C60% of the patients. An elevation of IgG4 is frequently found. Corticosteroids and cyclophosphamide are classically used for remission induction, while Alas2 azathioprine and methotrexate are the therapeutic options for remission maintenance. B-cell depletion with rituximab has shown promising results for remission induction. Keywords: eosinophilic granulomatosis with polyangiitis, vasculitis, eosinophils, vascular diseases, ANCA-associated vasculitis Introduction and Epidemiology Eosinophilic granulomatosis with polyangiitis (EGPA) is a multisystemic disorder, belonging to the small vessel anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAVs). According to the 1994 Chapel Hill consensus conference (CHCC), EGPA is defined as an eosinophil-rich and granulomatous inflammation often involving the respiratory tract, and necrotizing vasculitis predominantly affecting small to medium-sized vessels, associated with asthma and eosinophilia. Formerly known as ChurgCStrauss syndrome, this eponym has been replaced during the 2012 Pyrotinib dimaleate Revised International CHCC, with the aim of focusing on the histopathology of the disease (1). Unlike in the 1990 American College of Rheumatology classification criteria and the former CHCC, the CHCC 2012 has reported for the first time that ANCA are found in EGPA, especially in patients with glomerulonephritis. This reflects some of the newest evidences of the distinction of two EGPA subsets, depending on the presence or the absence of ANCA (Table ?(Table1)1) (2). Table 1 Diagnostic criteria, classification, and nomenclature of eosinophilic granulomatosis with polyangiitis during the last 20?years. and *(5) and with (6). This contraction of the class II HLA repertoire suggests a strong CD4+ T lymphocyte activation, possibly triggered by allergens or antigens. It has been also investigated the presence of single nucleotide polymorphisms (SNP) of the gene, which encodes interleukin (IL)-10, an important molecule for the activation of the Th-2 pathway; EGPA ANCA-negative subset has been associated with the IL10.2 haplotype of the IL-10 promoter gene, a condition, which leads to an increased production of IL-10 (7). This is apparently in line with EGPA pathogenesis, which is characterized by an increased Th-2 response and an increase in IgG4 levels, both of which seem to be mediated by IL-10. Acquired determinants Some environmental triggers have been identified: the exposure to different allergens, infections, vaccinations could trigger the disease. Drugs may also have a pathogenetic role and, among these, the leukotriene receptor antagonists are the most frequently involved more often used as steroid-sparing agents for asthma, their key role in triggering EGPA is still uncertain (8). More Pyrotinib dimaleate recently, also the recombinant anti-IgE monoclonal antibody omalizumab used in patient with asthma has been considered as an EGPA trigger (9C11). According to the most reliable hypotheses, both LTRA and anti-IgE antibody may be involved in EGPA pathogenesis simply unmasking the disease, due to the delayed use of steroids. A recent review has shown the possible pathogenetic influence of silica exposure in AAVs, including EGPA (12). Eosinophils The part of the eosinophils is still uncertain in EGPA but different studies have shown the cytotoxic (13, 14) and pro-coagulant (15, 16) properties of this cell type, which may result in the development of cardiovascular and cerebrovascular complications in individuals with any type of hypereosinophilic syndromes including EGPA. Although they are usually considered to be effector cells, they may act as immunoregulatory cells (2): indeed, a cross-talk between Pyrotinib dimaleate T-lymphocytes and eosinophils has been pointed out. In a recent study, high concentrations of IL-25 have been recognized in the sera of EGPA individuals; eosinophils are the main source of IL-25, which induces T-cells to produce cytokines that stimulate Th-2 and, at the same time, eosinophilic reactions (17). T-lymphocytes It has been shown that T-lymphocytes have an important part in the EGPA pathogenesis. T-cells are present in the most of the organ lesions and in some of them, like peripheral neuropathy, they represent the main component. Moreover, serum levels of T-cell activation markers, like IL-2r, are improved during the active phase of the disease (18). T-cells receptors display a restricted repertoire suggesting oligoclonal development (19), which is definitely good hypothesis of an antigen-driven disease. Clonal restricted effector CD8+ lymphocytes having a proinflammatory profile have.