Recently, the Department of Nephrology of Nanshan Hospital successfully treated an elderly patient with microscopic polyangiitis and acute nephritis (crescentic nephritis), who is recovering well and was discharged from the hospital. The patient is a 77-year-old male who was admitted to our emergency ICU due to “hemoptysis for 3 days”; after admission, the patient continued to hemoptysis, about 20-30ml per day; blood creatinine continued to be elevated; blood count showed moderate anemia; chest X-ray showed: bronchial dilatation and infection in both lower lungs; chest CT: 1. The chest CT: 1. multiple bronchial and fine bronchial dilatation in both lungs, a little perifocal inflammation or alveolar blood accumulation, multiple focal foci of fibrous calcification in the left lung, multiple pulmonary blisters in both lungs; 2. occupying lesions in the dorsal segment of the lower lobe of the right lung not excluded. The patient had a history of “duodenal bulb ulcer” 14 years ago. The patient was treated with anti-infection and hemostasis in the emergency ICU, but his symptoms did not resolve and his blood creatinine continued to rise progressively, so he was transferred to the nephrology department for further treatment. Further examination by the nephrology department revealed that the vasculitis antibody profile was positive for MPO-ANCA; the electronic gastroscopy showed multiple ulcers in the duodenal bulb; the renal function showed that the blood creatinine was elevated to 613 umol/L, hemoptysis persisted, and he had less urine and increased edema in both lower limbs. The patient was 77 years old, with hemoptysis and multiple ulcers in the duodenal bulb, and the condition was complicated and difficult to treat. In order to clarify the diagnosis and develop the best treatment plan, the nephrology department performed a renal puncture biopsy (the oldest kidney biopsy patient in our hospital) for this elderly patient with the support of the director of ultrasound department, Li Galpin. On the next day of methylprednisolone shock treatment, the patient’s hemoptysis stopped, blood creatinine gradually decreased to 383umol/L, urine output increased, and lower limb edema gradually decreased. After 1 month of follow-up, the patient’s blood creatinine gradually decreased to 252 umol/L, urine output was normal, and there was no edema in both lower limbs. Microscopic polyangiitis (MPA), an autoimmune disease, is a systemic, necrotizing vasculitis that mainly affects small blood vessels and is characterized by the absence or small amount of immune complexes deposited in the vessel wall. The clinical manifestation of the disease is necrotizing glomerulonephritis, for which there is a lack of uniform diagnostic criteria internationally. The patient presented prominently with pulmonary capillaritis (hemoptysis) and acute nephritis (crescentic glomerulonephritis) with multiple ulcers in the duodenal bulb, which was very difficult to treat and had a high risk of complicating gastrointestinal bleeding. We improved the pathological examination by timely renal biopsy to clarify the diagnosis and gave timely treatment with hormones, cyclophosphamide and strong gastric protection to rapidly alleviate the progression of the disease and achieve a good treatment effect. We will follow up and follow up this patient for a long time.