There is no special precursor of adult leukemia, but leukemia can generally manifest as anemia, bleeding, fever and other symptoms. 1. Anemia: 70% of patients have anemia as the first symptom, which is often progressive and disproportionate to the degree of bleeding. 2. Bleeding: half of the patients have bleeding phenomenon at the initial diagnosis, such as skin petechiae, ecchymosis and bleeding gums, nosebleeds and so on. 3. Fever: 50% of patients have fever as an early manifestation, often due to infection. Commonly, it is respiratory tract infection, lung infection, enteritis, perianal abscess and so on. In addition to the above signs, tissue infiltration may also occur in a small number of adult leukemia patients in the early stage. If the above symptoms occur, it is recommended to go to the hospital as soon as possible, under the guidance of the doctor to clarify the cause of the disease and carry out regular treatment.