Eosinophilic granulomatosis with polyangiitis (EGPA) is a rare multisystem immune-mediated vasculitis with damage to medium and small vessels (including capillaries, venules and veins), first described in 1951. The etiology and pathogenesis of this disease associated with a combination of immunocomplex and allergic mechanisms have not been fully studied, and there are no generally accepted techniques to initial therapy. The diversity of the clinical picture at the disease onset, the gradual manifestation of signs, the need to take into account not only clinical but also laboratory parameters, makes it difficult to make a correct diagnosis in the early stages. This article describes a clinical case of a relatively late diagnosis of EGPA, which may be due to a lack of practitioner awareness about such a rare disease and a late referral to a rheumatologist. Not only morphological verification and immunological tests of patients can speed up diagnosis, but also discussion of such clinical cases in the medical community. Currently, the EGPA therapy possibilities have been expanded by including the disease in indications for biological treatments aimed at interleukin 5, which will improve the disease prognosis and reduce the burden of long-term hormonal therapy. KEYWORDS: eosinophilic granulomatosis with polyangiitis, vasculitis, eosinophilia, differential diagnosis, bronchial asthma, clinical case. FOR CITATION: Karoli N.A., Kanaeva T.V., Nikitina N.M. Difficulties in diagnosing eosinophilic granulomatosis with polyangiitis in clinical practice. Russian Medical Inquiry. 2024;8(3):171–175 (in Russ.). DOI: 10.32364/2587-6821-2024-8-3-8.