The causes of hemoptysis are as follows: 1) bronchial lesions: such as bronchial tuberculosis, bronchiectasis, bronchial tumors, etc.; 2) pulmonary lesions: such as pulmonary tuberculosis, pulmonary tumors, pulmonary abscesses, etc.; 3) cardiac lesions: such as mitral stenosis, which can also cause hemoptysis; 4) rheumatic diseases: such as arteritis, aortitis, pulmonary renal syndrome, etc., which can also cause large amounts of hemoptysis; 5) hematologic lesions: such as leukemia, idiopathic thrombocytopenic purpura, etc., which can cause changes in the coagulation status, leaving the blood in a hypocoagulable state, which can also manifest as hemoptysis.