The early (prodromal) stage is marked by airway inflammation; almost all patients experience asthma and/or allergic rhinitis.

The second stage is characterized by abnormally high numbers of eosinophils (hypereosinophilia), which causes tissue damage, most commonly to the lungs and the digestive tract.

[7] The signs and symptoms of hypereosinophilia may include weight loss, night sweats, asthma, cough, abdominal pain, and gastrointestinal bleeding.

[2][needs update] The French Vasculitis Study Group has developed a five-point system ("five-factor score") that predicts the risk of death in Churg–Strauss syndrome using clinical presentations.

[20] On CT scan of the lungs, peripheral parenchymal opacification (pulmonary consolidation or ground-glass opacity) in the middle and lower zones is the predominant pattern.

[21] Treatment for eosinophilic granulomatosis with polyangiitis includes glucocorticoids (such as prednisolone) and other immunosuppressive drugs (such as azathioprine and cyclophosphamide).

[22] On 12 December 2017, the FDA approved mepolizumab, the first drug therapy specifically indicated for the treatment of eosinophilic granulomatosis with polyangiitis.

[24] In addition to mepolizumab, a number of emerging targeted biotherapies—including the anti-IgE monoclonal antibody omalizumab, immunomodulation with Interferon-α, and B cell therapy with rituximab—may lead to increasingly personalized treatment regimens for future EGPA patients.

[25] On 18 September 2024, AstraZeneca announced FDA approval for Fasenra (benralizumab), a biologic drug therapy indicated for use in adult patients with EGPA, following the MANDARA Phase III trial results.

Published in The New England Journal of Medicine, the first head-to-head non-inferiority trial of biologics in patients with relapsing or refractory EGPA measured the efficacy and safety of Fasenra against mepolizumab.

[29] The memoir Patient, by musician Ben Watt (of Everything but the Girl fame), deals with his experience with EGPA in 1992, and his recovery.

His treatment required the removal of 5 m (15 ft) of necrotized small intestine (about 75%), leaving him on a permanently restricted diet.

[30] Umaru Musa Yar'Adua, the president of Nigeria from 2007 to 2010, reportedly had EGPA and died in office of complications of the disease.

[32] Japanese ski jumper Taku Takeuchi, who won the bronze medal in the team competition in 2014, has the disease and competed at the Sochi Olympics less than a month after being released from hospital treatment.

[36] American professional basketball player Willie Naulls died on 22 November 2018 in Laguna Niguel, California, from respiratory failure due to EGPA,[37] which he had been battling for eight years.