Coughing up sputum that is brown in color is mostly caused by a small amount of blood cells in the sputum and is mainly considered to be caused by respiratory tract diseases. It is more commonly caused by lung cancer, tuberculosis, bronchiectasis or lobar pneumonia. The typical symptom of lobar pneumonia is coughing up rusty sputum. These inflammations can also irritate the local area, which can cause the rupture of small blood vessels and easily cause a small amount of bleeding, which is also easily accompanied by fever, cough, chest pain, and even dyspnea, shortness of breath, and chest tightness. There is a small amount of bleeding that is not discharged in time can also form stale blood, and the color can also form such phlegm after it is discharged through coughing. Usually you need to go to the hospital for examination and treat with medication under the guidance of the doctor according to the examination results.