Introduction. One of the distinguishing features of systemic vasculitis is their manifestation under the guise of a lesion of one or another organ system, which is often multi-organ in nature with signs of systemic inflammation. The latter is interpreted primarily as part of an infectious or paraneoplastic process, which causes a delay in the diagnosis.The aim of the study was to present the diversity of the clinical picture in vasculitis associated with antineutrophil cytoplasmic antibodies (ANCA), the speed and large volume of diagnostic measures with the effective cooperation of therapeutic and surgical specialists, radiologists on the way to verifying granulomatosis with polyangiitis in a young woman.Materials and methods. Patient K., 46 y. o., was hospitalized in the Otolaryngology Department of the N.I. Pirogov City Clinical Hospital No. 1 of the Moscow Health Department with complaints of hearing loss, pain and stuffiness in the left ear, unproductive cough, hoarseness and fever up to 38.5 °C. According to the radiography (RG) of the chest organs, right-sided pneumonia was detected. Conducted antibiotic therapy without effect. As part of the differential diagnostic search, the following nosologies were excluded: infective endocarditis, sepsis, tuberculosis, primary multiple or central lung cancer complicated by paracancer pneumonia, metastatic lesion, infectious, brucellosis spondylodiscitis.Results. In the blood test, attention was drawn to a decrease in the level of hemoglobin to 111 g / l, an increase in the rate of erythrocyte sedimentation to 45 mm / h and the level of C-reactive protein to 142 mg / l, microhematuria according to the general urine analysis. Instrumental research methods – RG of 16.02.22, MSCT of the chest organs on 17.02.22, 27.02.22, 10.03.22 showed progressive bilateral focal pneumonia with a focus of consolidation in the middle lobe, EchoCG, ultrasound of the abdominal cavity and small pelvis, RG of the temporal bone, bronchoscopy with bronchoalveolar lavage and microscopic analysis, for atypia and bacteriological culture. A gynecological examination and a smear from the cervical canal for microscopic analysis were performed, atypical cells, consulted by a phthisiatrician (no data for tuberculosis), consulted three times by a thoracic surgeon (exclusion of volumetric formation of the middle lobe of the right lung). Given the history and clinical presentation (female gender, young age, bilateral otitis media, hoarseness, and destructive nature of pneumonia), granulomatosis with polyangiitis was suspected, and tests for ANCA were prescribed. A transthoracic biopsy of the right lung was performed. A rheumatologist prescribed induction pulse therapy with corticosteroids, and after serological and histological confirmation (antibodies to Proteinase-3 Anti-PR3 > 200 IU / ml, productive pneumonitis, granulomas without signs of tuberculosis), immunosuppressive therapy with cyclophosphamide. Against the background of pathogenetic treatment, a pronounced clinical and laboratory effect was noted.Conclusion. In this clinical situation, the simultaneous involvement of specialists of various profiles, the performance of a large number of laboratory and instrumental studies in dynamics, the absence of delay in histological verification made it possible to quickly exclude common diseases in the population and suspect systemic vasculitis, establishing a correct diagnosis within 5 weeks of the hospitalization period.