Recommendations: 1. Eosinophilic granulomatous polyarteritis should be seen at or in collaboration with a center with experience in small to medium vessel vasculitis. Our recommended differential diagnostic tests are, at a minimum, serologic testing for toxoplasmosis and AIDS, Aspergillus-specific IgE and IgG levels, sputum and/or bronchoalveolar lavage for Aspergillus, trypsin-like and vitamin B12 levels, peripheral blood smears (for dysplastic eosinophils or mother cells), and chest CT; additional tests are based on the patient’s specific clinical presentation. Additional tests need to be based on the patient’s specific clinical presentation, and a comprehensive search for the cause of elevated eosinophils should be performed. 3. Encourage the acquisition of biopsies from patients with suspected eosinophilic granulomatous polyarteritis. ANCA testing (indirect immunofluorescence and ELISA) should be performed in patients with suspected eosinophilic granulomatous polyarteritis. 5. There are no reliable biomarkers to assess the disease activity of suspected eosinophilic granulomatous polyarteritis. Once EGPA is diagnosed, it is recommended to evaluate the lungs, kidneys, heart, GI tract, and/or peripheral nerves that may be involved. 7. Define remission of eosinophilic granulomatous polyarteritis: absence of clinical systemic manifestations (except asthma and/or ear, nose and throat). 8. Define relapse of eosinophilic granulomatous polyarteritis: the presence of clinical manifestations of eosinophilic granulomatous polyarteritis (except asthma and/or ear, nose and throat) or relapse or worsening of eosinophilic granulomatous polyarteritis requiring additional, altered or increased doses of glucocorticoids and/or immunosuppressive agents. 9. To achieve remission of eosinophilic granulomatous polyarteritis, glucocorticoids are indicated; those with organ- or life-threatening clinical manifestations should be given prednisone 1 mg/kg/day, recommendation level A. 10. Patients with life- and/or organ-impairing manifestations (e.g., cardiac, gastrointestinal, central nervous system, severe peripheral neuropathy, severe ophthalmopathy, alveolar hemorrhage, and/or glomerulonephritis) should be treated with glucocorticoids and additional immunosuppressive agents. corticosteroids and an additional immunosuppressive regimen (e.g., cyclophosphamide) to induce remission. Maintenance therapy (with azathioprine or methotrexate) is recommended for those with life- and/or organ-impairing manifestations of remission-inducing therapy. Grade C 12. Glucocorticoids alone may be appropriate in patients without manifestations of life and/or organ damage; additional immunosuppressive agents may be considered selectively for those who cannot reduce the glucocorticoid dose to 7 or 5 mg/day after 3-4 months of treatment or for those who relapse. Recommendation Grade C 13. Plasma exchange is usually not effective in eosinophilic granulomatous polyarteritis, but may be considered selectively for ANCA-positive rapidly progressive glomerulonephritis or pulmonary-renal syndrome. Recommendation Grade D 14. Rituximab may be considered for selective use in patients with ANCA-positive renal involvement or refractory disease. Grade C 15. Intravenous gammaglobulin may be considered in patients with eosinophilic granulomatous polyarteritis that has recurred during glucocorticoid (and/or other immunosuppressive) therapy in pregnancy and is resistant to other therapies; immunoglobulin replacement therapy may be considered in patients with drug-induced hypogammaglobulinemia with severe and/or recurrent infections. Recommendation Grade C 16. a-interferon may be used selectively as second- or third-line therapy in patients. Leukotriene receptor antagonists may be used, if needed, in patients with eosinophilic granulomatous polyarteritis. Inactivated vaccination against influenza and pneumococci should be encouraged; live attenuated vaccine is contraindicated in persons using immunosuppressive agents and/or prednisone doses ≥ 20 mg/day. Recommendation Grade D 19. Patient education is encouraged. Recommendation Grade D 20. Those with peripheral nerve involvement and motor nerve dysfunction should be routinely referred to a physical therapist. Recommendation Grade D 21. Patients should be advised to avoid smoking and stimulants. Recommendation Grade D 22. Venous thrombosis and pulmonary embolism should be treated according to general guidelines for the management of thrombotic disorders; it is not clear whether anticoagulation should be extended for those with recurrent or persistent disease. Recommendation grade D