Occasionally there is blood in sputum, after examination to temporarily exclude lung and large bronchial lesions, should also consider cardiovascular diseases, hematologic diseases, other systemic diseases. 1. Cardiovascular diseases: such as left heart failure, rheumatic heart disease or congenital heart disease, pulmonary hypertension caused by valvular disease, etc., can also lead to symptoms of blood in sputum. 2. Hematologic diseases: diseases with systemic bleeding tendency, such as thrombocytopenic purpura and coagulation disorders. If there is respiratory tract damage, blood in sputum may also occur. 3. Other systemic diseases: autoimmune diseases involving the respiratory system, such as systemic small vessel vasculitis, systemic lupus erythematosus; bleeding caused by lesions in the nasal cavity, oral cavity and pharynx, blood flowing into the mouth causing coughing, mistaken for respiratory bleeding. Occasional blood in the sputum may also be related to dry weather and coughing causing capillary rupture. In addition to this, there are other diseases that can cause blood in sputum. If the patient’s symptoms are not relieved or aggravated, he or she should immediately seek medical attention, complete the examination, make a clear diagnosis, and provide targeted treatment.