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MRI abnormalities must be interpreted prudently, as the meaning of T1-weighted cardiac MRI abnormalities remains unknown for asymptomatic patients. Indeed, among a series of 42 non-cardiomyopathic (diagnosed independently of MRI ndings) EGPA patients, those with cardiac MRI abnormalities had EGPA outcomes similar to those without. Thus, cardiac MRI alone cannot be used to diagnose cardiomyopathy [51, 52]. In certain situations, coronary arteriography might be useful to distinguish EGPA cardiomyopathy from the underlying ischemic cardiopathy.

Diagnosis

Diagnostic Criteria

Initially, the three EGPA-de ning histological lesions mentioned above served as the basis of the diagnosis. However, because the simultaneous presence of all three lesions types is uncommon, EGPA diagnosis remained clinical. In 1984, Lanham et al. devised the following criteria: asthma, blood eosinophilia >1500/mm3, and clinical or pathological evidence of vasculitis involving at least two organs [34]. However, because asthma onset can follow the vasculitic phase and because blood eosinophil counts may fuctuate, these criteria could lack sensitivity.

Thus, the 1990 ACR EGPA classi cation criteria [2] required at least four of the following criteria (Box 7.1): asthma, eosinophilia (>10% of white blood cell count), mononeuropathy or polyneuropathy, pulmonary in ltrates, paranasal sinus abnormality, and/or extravascular eosinophils. However, these descriptive criteria were established for clinical studies; they are not diagnostic.

The more recent 2012 Chapel Hill Consensus Conference Nomenclature has de ned EGPA as an “eosinophil-rich and necrotizing granulomatous infammation, frequently involving the respiratory tract, and necrotizing vasculitis predominantly affecting small-to-medium-sized vessels and associated with asthma and eosinophilia” [3].

Diferential Diagnosis

Clinical manifestations dictate the entities included in the differential diagnosis of EGPA. Prior to the onset of vasculitis manifestations, it may be dif cult to differentiate EGPA among eosinophilic asthma, parasitic infections, or allergic bronchopulmonary aspergillosis.

Idiopathic chronic eosinophilic pneumonia has no known etiology and is a rare disease with nonspeci c respiratory symptoms and eosinophilia [53–55]. Pertinently, it has no vasculitic and extrapulmonary signs and, thus, remains an exclusionary diagnosis.

Once vasculitis symptoms become overt, the main differential diagnoses are other systemic vasculitides, especially GPA and MPA. Although eosinophilia is also seen in GPA, EGPA can usually be differentiated by the presence of asthma, nondestructive ENT manifestations, and anti-MPO-­ ANCAs (as opposed to anti-PR3-ANCAs in GPA).

Hypereosinophilic syndrome (HES) can also be dif cult to distinguish from EGPA. Although HES can also be associated with cardiopathy, pulmonary manifestations, and/or nerve involvement, vasculitis symptoms are absent, as are histological signs of vasculitis [56]. Two HES variants are recognized: one is the lymphocytic variant, with a predominance of skin and soft tissue involvements, resulting from abnormal CD3−CD4+ T-cell subsets responsible for IL-5 synthesis [57], and the second is the myeloid form. Because HES myeloid variants have speci cally elevated tryptase and vitamin B12 levels, these biological determinations can be useful for excluding HES, the diagnosis of which can be con-rmed by genetic testing for FIP1L1–PDGFRA fusion and JAK2 mutations [58].

Recently, the EGPA Consensus Task Force experts have recommended complementary investigations to exclude the main differential diagnoses [59]: toxocariasis and human immunode ciency virus serology, speci c IgE and IgG dosages for Aspergillus spp., the search for Aspergillus spp. in sputum and/or BAL specimens, tryptase and vitamin B12 dosages, peripheral blood smears to look for dysplastic eosinophils or blasts, and thoracic CT scan.

In addition, asthma with eosinophilia is another entity in the differential diagnosis of EGPA. In the absence of extrapulmonary manifestations, making a distinction between therst EGPA manifestations and asthma with eosinophilia can be dif cult, especially when ANCAs are absent.

Prognosis and Outcomes

The use of glucocorticoids and immunosuppressants have revolutionized EGPA prognoses, with a 5-year survival rate rising from 10% in the 1950s to 90% today. However, prognoses for all EGPA patients differ according to the presence or absence of several clearly identi ed prognostic factors. Multivariate analyses of the characteristics of 260 polyarteritis nodosa and 82 EGPA patients, the foundation of the original 1996 prognostic FFS, retained 5 items signi cantly associated with mortality and accorded each presence with 1 point: proteinuria >1 g/day; gastrointestinal bleeding, perforation, infarction, and/or pancreatitis; renal insuf ciency (with serum creatinine >1.58 mg/dL or 140 μmol/L); central nervous system involvement; and cardiomyopathy. FFS = 0, 1, or 2 corresponded to respective 5-year mortality rates of 12%, 26%, or 46%. The FFS was revisited in 2011, and, this time, it was based on the analysis of 1108 vasculitis patients

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