Aim. To present a clinical case of late diagnosis of granulomatosis with polyangiitis (GPA), which for a long time was interpreted as a pulmonary form of tuberculosis with the passage of anti-tuberculosis therapy without effect, which led to severe structural changes and resection of the lungs and deformation of the bones of the facial skeleton.Materials and methods. Patient S., 31 y. o., was hospitalized in the rheumatology department with complaints of bloody discharge from the nose with the formation of crusts, hearing loss on both sides, weakness, nose deformity. From the anamnesis: in 2012, a cough with mucous sputum appeared. During examination at the Center for Combating Tuberculosis, on the basis of multiple rounded foci of both lungs, despite a negative diaskin test and the absence of mycobacterium tuberculosis in the sputum analysis, infiltrative tuberculosis was diagnosed. For two years, combined therapy with anti-tuberculosis drugs was carried out. In 2013, a staged combined resection of the left lung was performed; in 2014, a resection of the lower lobe of the right lung was performed. In 2015, nasal discharge increased, large crusts began to stand out, followed by bleeding, and a change in the shape of the nose was observed. In 2016, due to hearing loss in the left ear, he turned to an otorhinolaryngologist, diagnosed with ulcerative necrotic rhinitis, perforation of the nasal septum. Antibiotic therapy - no effect. Blood tests revealed positive antibodies to proteinase-3. In March 2017, he was hospitalized in the rheumatology department.Results. There were CT signs of fibrotic changes in the lungs with calcifications, areas of compaction of the “frosted glass” type in the upper lobes of the lungs. Laboratory examination revealed positive antibodies to proteinase-3, decreased glomerular filtration and tubular reabsorption. Analysis of the biopsy material from the lung and nasal mucosa revealed morphological signs of granulomatosis with polyangiitis. For the first time in 5 years, granulomatosis with polyangiitis was diagnosed, generalized form, chronic course, moderate activity, with damage to the upper respiratory tract (pansinusitis, rhinitis, chronic bilateral adhesive otitis media), lungs (nonspecific interstitial pneumonia), kidneys (microhematuria, proteinuria), joints (arthralgia). The activity index according to the Birmingham BVAS scale is 16 points, the VDI organ damage index is 6 points. In a retrospective analysis, tuberculosis was not confirmed. Therapy with prednisolone, cyclophosphamide (endoxan), biseptol was carried out, against which the patient's condition improved significantly.Conclusion. The presented clinical case demonstrates the difficulties of differential diagnosis of GPA with other granulomatous processes. Late diagnosis led to damage to vital organs: lungs, kidneys, deformity of the back of the nose, which, most likely, could have been avoided in case of timely diagnosis and early initiation of adequate therapy. As a result of an erroneous diagnosis at the onset of the disease, the patient underwent unjustified resection of both lungs twice. Timely diagnosis of the granulomatous process with the involvement of several pathologists as experts, including those with a torpid course of pulmonary tuberculosis, significantly improves the prognosis of patients and avoids fatal complications.