How to distinguish acute leukemia from chronic leukemia? The differences between the two are described below in terms of pathogenesis, disease course, clinical manifestations, and laboratory tests.
Leukemia can be classified as acute or chronic according to the disease course and the maturity of leukemic cell differentiation;
- Acute leukemia naturally has a short course, rapid onset, and leukemic cells are predominantly more primitive naïve cells;
- Chronic leukemia has a long natural course and a slow onset, with predominantly mature leukemic cells.
According to the type of leukemia cells, there are two categories of leukemia: lymphocytic leukemia and myeloid leukemia. Accordingly, leukemias can be classified into four types:
- Acute lymphoblastic leukemia (ALL)
- Acute myeloid leukemia (AML)
- chronic lymphocytic leukemia (CLL)
- Chronic myelogenous leukemia (CML)
Clinical presentation
- Acute leukemia is characterized clinically by infection, hemorrhage, anemia, and infiltration of extramedullary tissues and organs, and the disease tends to progress rapidly.
- Chronic myeloid leukemia is often diagnosed asymptomatically or by incidental physical examination with leukocytosis or left upper abdominal mass. Common clinical signs and symptoms include malaise, excessive sweating, abdominal distention, loss of appetite, and wasting; physical examination mostly shows splenomegaly, even giant spleen. Chronic lymphocytic leukemia is highly prevalent in the elderly and may be asymptomatic or weak, fatigue, night sweats, low-grade fever, painless lymph node enlargement, and also hepatomegaly and splenomegaly.
Laboratory tests
Hematological examination
- White blood cells may be significantly increased or decreased on routine blood tests in patients with acute leukemia, and abnormal cells (leukemia cells) may be found in peripheral blood, along with decreased hemoglobin and platelets;
- Patients with chronic granulocytic leukemia have increased peripheral blood leukocytes (generally >50×10^9/L), classification can be seen in all stages of naïve granulocytes, predominantly intermediate and late juvenile granulocytes with a bias toward maturity, increased proportion of eosinophils and basophils, mostly normal or increased platelets, and normal or mildly decreased hemoglobin; patients with chronic lymphocytic leukemia have absolute peripheral blood lymphocyte values >5×10^9/L for more than 4 weeks, predominantly mature lymphocytes, decreased hemoglobin and platelets in about 30% of patients, positive anti-human globulin test in about 20%, and autoimmune hemolysis in 8%.
Bone marrow examination
Different types of leukemia have different characteristic bone marrow manifestations, for example:
- Acute promyelocytic bone marrow chromosome with characteristic PML/RARa fusion gene formed by translocation of chromosome 15,17;
- Chronic granulocytic leukemia can have characteristic Philadelphia chromosome alterations, namely BCR/ABL fusion gene formed by translocation of chromosome 9,22.