The article presents clinical observations demonstrating the difficulties of diagnostic search in establishing the diagnosis of systemic vasculitis associated with antineutrophil cytoplasmic antibodies, which include a rare disease eosinophilic granulomatosis with polyangiitis (ChurgStrauss syndrome). Carefully collected anamnesis, participation of specialists of different profiles, retrospective analysis of laboratory and instrumental data allowed to verify the diagnosis, to prescribe adequate therapy. The aim of the publication is to discuss the need for early diagnosis of eosinophilic granulomatosis with polyangiitis, which can improve the effectiveness of therapy and improve the overall prognosis for this disease, taking into account modern approaches based on the main provisions of international recommendations that were prepared in 2015 with the participation of leading experts from Europe, USA and Canada and were called to become the basis for choosing a personalized patient therapy strategy. In some cases, the diagnosis of eosinophilic granulomatous polyangiitis is complicated by the diversity of the clinical picture, the non-simultaneous appearance of the main symptoms and the violation of the stages of the process. In the differential diagnosis of systemic vasculitis, assessment of initial clinical manifestations, testing for the presence of antibodies to the cytoplasm of neutrophils, multispiral computed tomography of the chest organs and diagnostic biopsy of the affected tissues are crucial. In the histological conclusion, a picture of focal ulcerative-necrotic lesions of the nasal mucosa with signs of vasculitis and a pronounced eosinophilic cell component of inflammation was noted. The distinctive features of this case include the onset of the disease with the development of myocardial infarction and early damage to the hearing organ in the form of cochlear neuritis, complicated by sensorineural hypoacusis. The combination of high doses of glucocorticosteroids and cyclophosphamide is still the gold standard for the treatment of severe cases, but the use of biological agents such as rituximab or mepolizumab seems to be a promising therapeutic alternative (4 figs, bibliography: 3 refs).