The causes of haemoptysis are as follows: 1) bronchial lesions: e.g. bronchial tuberculosis, bronchiectasis, bronchial tumours, etc.; 2) intrapulmonary lesions: e.g. pulmonary tuberculosis, intrapulmonary tumours, lung abscess, etc.; 3) cardiac lesions: e.g. mitral stenosis, which can also cause haemoptysis; 4) rheumatic diseases: e.g. arteritis, aortitis, pulmonary renal syndrome, etc., which can also cause large amounts of haemoptysis; 5) haematological lesions: e.g. leukaemia, idiopathic thrombocytopenic purpura, etc., which can cause changes in the coagulation status, leaving the blood in a hypocoagulable state, which can also manifest as haemoptysis.