Microscopic polyangiitis is a very rare disease characterized by the lesions of arteriolae, venulae and capillaries--mainly of the kidneys and lungs, but also of other systems and organs. The elevated titer of anti-myeloperoxidase ANCA is very important immunological indicator. The main changes in our patient were related to the lung bleeding and rapidly progressive glomerulonephritis. The treatment has started according to the standard Fauci scheme adjusted to the level of disease severity and the age of patient (prednisone 60 mg/24 h, along with the gradual dosage decrease, cyclophosphamide 150 mg/24 h) and has lead to the clinical-laboratory remission. The patient had the leukocyte values irregularly controlled during the immunosuppressive therapy and agranulocytosis thus caused was not spotted in time, leading to the inadequate treatment of pneumonia that brought on the lethal outcome.