A persistent low fever with a cough that does not go away is not necessarily leukemia. Some patients with leukemia have fever as an early manifestation and can develop a low-grade fever, but infections, tuberculosis and other diseases can also lead to prolonged low-grade fever and cough. Cough is most often seen in respiratory diseases, such as bronchitis, asthma, and lung tumors, and less often in leukemia. There are many causes of low-grade fever. If the fever is prolonged for more than two weeks, it is called fever of unknown origin, such as rheumatic immune diseases, rare types of infections, and hematological tumors, such as leukemia and lymphoma. Patients with acute leukemia usually present with a high fever that progresses rapidly, with typical symptoms arising after several months, such as anemia and leukopenia. Chronic leukemia, especially chronic lymphocytic leukemia, may present with prolonged low-grade fever combined with anemia and bleeding symptoms, and routine blood tests suggesting significant abnormalities in white blood cells, hemoglobin and platelets. However, patients with tuberculosis, rheumatic diseases, hyperthyroidism, and anemia can also cause persistent hypothermia. Therefore, prolonged cough with low fever may not necessarily be leukemia. Factors such as routine blood tests, thyroid function, blood sedimentation, and rheumatic series need to be checked to clarify the cause.