The precursor manifestations of leukemia include bone pain, unexplained fever, bleeding spots or bruises on the skin, and fatigue. 1. In the early stage of leukemia, leukemia cells (primitive and naïve cells) in the bone marrow proliferate in large numbers, but have not yet been released into the peripheral blood. At this time, the patient will have unexplained bone pains, and swelling pains of the femur, tibia or sternum are more common. 2. Abnormal proliferation of leukemia cells in the bone marrow will inhibit the production of normal cells at the same time, which will lead to anemia and significantly lower platelet counts, and the patient may experience weakness, skin bleeding spots or bruises. 3. Some patients with leukemia have abnormally high white blood cell counts, i.e. hyperleukinemia, and may have chest tightness and respiratory difficulties; while some patients have severely reduced white blood cell and granulocyte counts, or even granulocyte deficiencies, and may have unexplained fever. When patients have the above symptoms, they need to go to the Department of Hematology in time to get a clear diagnosis and targeted treatment under the guidance of physicians.