Most acute leukemias in children and adolescents have a rapid onset. Common first symptoms include fever, progressive anemia, significant bleeding tendency or bone and joint pain. The slow onset of acute leukemia is mostly seen in elderly and some young patients, with progressive disease. In addition, a few patients can have convulsions, blindness, toothache, gum swelling, pericardial effusion, and bilateral lower limb paraplegia as the first symptoms. 1. Fever is one of the most common symptoms of leukemia, manifesting as different degrees of fever and febrile patterns. The main cause of fever is infection, among which pharyngitis, stomatitis and perianal infection are the most common, and pneumonia, tonsillitis, gingivitis and perianal abscess are also more common. Ear inflammation, enteritis, carbuncle, pyelonephritis, etc. can also be seen, and sepsis and septicemia can occur in severe cases. Fever can also be a symptom of acute leukemia itself, without any signs of infection. 2., Infections Pathogens are mostly bacterial. In the later stages of the disease, the possibility of fungal infections gradually increases due to prolonged below-normal granulocytes and the use of broad-spectrum antibiotics. Viral infections are rare but dangerous and should be noted. 3, bleeding Bleeding sites can spread throughout the body, the skin, gums, nasal bleeding is the most common, there can also be retinal, ear bleeding and intracranial, gastrointestinal, respiratory and other visceral hemorrhage. Excessive menstruation is also common in women and can be the first symptom. 4. Anemia can appear at an early stage, and in a few cases, myelodysplastic syndrome (MDS) can appear months or years before the diagnosis, and then develop into leukemia. Patients often have symptoms such as weakness, pallor, palpitations, shortness of breath, and edema of the lower extremities. Anemia is seen in all types of leukemia and is more common in older patients. 5. Bone and joint pain Leukemic infiltration of bone and periosteum causes bone pain, which can be diffuse in the limbs or back, or limited to joint pain, often resulting in difficulty moving. More than 1/3 of patients have sternal pressure pain, and this sign helps to diagnose the disease. 6, liver, spleen and lymph node enlargement Mild to moderate hepatosplenomegaly is common. the incidence of hepatosplenomegaly is higher in ALL than in AML, and splenomegaly is more common and more pronounced in chronic than in acute leukemia. Lymph node enlargement is also more common in ALL than AML, and can involve superficial or deep lymph nodes such as mediastinum, mesentery, retroperitoneum, etc. 7.Central nervous system leukemia (CNSL) CNSL is a serious complication of acute leukemia, commonly seen in ALL and M4 and M5 in AML, but other types can also be seen. CNSL has become a blind spot and a difficulty in the treatment of modern acute leukemia because of the difficulty of crossing the blood-brain barrier with commonly used chemotherapeutic drugs. The infiltration site mostly occurs in the arachnoid and dura mater, followed by the brain parenchyma, choroid or cranial nerves. In severe cases, there are typical manifestations of increased intracranial pressure such as headache, vomiting, strong collar, optic papilla edema, and even convulsions and coma, which may resemble intracranial hemorrhage, while mild cases only complain of mild headache and dizziness. The involvement of cranial nerves (VI and VII pairs of cranial nerves mainly) may lead to visual impairment and facial paralysis. 8. Other tissue and organ infiltrates ALL skin infiltrates are less common than AML, but testicular infiltrates are more common. Testicular leukemia is also often seen in ALL in remission, manifesting as painless enlargement of the testes unilaterally or bilaterally, with a firm texture without tenderness, and is second only to CNSL as a source of extramedullary recurrence of leukemia. Leukemic infiltration can also involve various tissues and organs such as lung, pleura, kidney, digestive tract, heart, brain, uterus, ovary, breast, parotid gland and eye, and show dysfunction of corresponding organs. The symptoms of chronic granulocytic leukemia start slowly and there are often no conscious symptoms in the early stage, and the diagnosis is only confirmed by abnormal blood picture or splenomegaly during health checkups or visits to the doctor for other diseases. As the disease progresses, signs of hypermetabolism such as fatigue, low fever, excessive sweating or night sweats, and weight loss may appear. Symptoms such as left upper abdominal cramping and fullness after eating due to splenomegaly may also appear. The most prominent feature on examination is splenomegaly, which often reaches the level of the umbilicus by the time the patient is seen. The disease can be stable for 1 to 4 years, and then enters an accelerated phase with rapid onset of anemia and more symptoms, and then quickly enters an acute phase, which can become AML or ALL.