Last reviewed: 28 Aug 2023
Last updated: 02 Jun 2023

This page compiles our content related to leukemia. For further information on diagnosis and treatment, follow the links below to our full BMJ Best Practice topics on the relevant conditions and symptoms.



A malignant clonal disease that develops when a lymphoid progenitor cell becomes genetically altered through somatic changes and undergoes uncontrolled proliferation. This progressive clonal expansion eventually leads to acute lymphoblastic leukemia (ALL), characterized by early lymphoid precursor cells replacing the normal hematopoietic cells of the bone marrow and further infiltrating various body organs. ALL can occur at any age, but more than half of all cases (53.5%) are diagnosed in those ages under 20 years.[4] It accounts for approximately 11% of leukemias and 0.3% of all cancers in the US.​​[5][6]​​ There are two forms of ALL: B-ALL (arising from B lymphoid progenitors), and T-ALL (arising from T lymphoid progenitors). B-ALL is more common.[7]​​ Most patients have signs and symptoms related to cytopenias (e.g., fatigue, easy bruising) at initial presentation and diagnosis. Enlarged lymph nodes can be an initial presenting cause. Genetic abnormalities in ALL include chromosomal rearrangements (e.g., translocations) detected by cytogenetic analysis, or other genetic lesions detected by molecular analysis. Cytogenetic abnormalities may be of prognostic and therapeutic significance.

An indolent lymphoproliferative disorder in which monoclonal B lymphocytes (>5000 cells/microliter [>5 x 10⁹/L]) are predominantly found in peripheral blood.[8] These lymphocytes can infiltrate the lymphatic system and hematopoietic organs such as the liver, spleen, and bone marrow. Age over 60 years is a key risk factor. Lymphadenopathy, splenomegaly, shortness of breath and fatigue are key diagnostic factors.[9]​​​​​ Patients may present with absolute lymphocytosis as an incidental finding on routine complete blood count (CBC); chronic lymphocytic leukemia is diagnosed by CBC with differential, blood smear showing smudge cells, and flow cytometry.​​[9][10]​​​​ 

Caused by the clonal expansion of myeloid blasts in the bone marrow, peripheral blood or extramedullary tissues. Occurs predominantly in older adults.[5] Common findings are pallor, ecchymoses and petechiae. Although most patients achieve complete remission, a high incidence of relapse leads to poor overall survival. Many subtypes exist, of which acute promyelocytic leukemia merits specific management.

A malignant clonal disorder of the hematopoietic stem cell that results in marked myeloid hyperplasia of the bone marrow.[11] Incidence peaks between the ages of 65 and 74 years, but people of all ages can be affected.[12] Exposure to ionizing radiation is associated with increased risk for chronic myeloid leukemia.[13] Possible symptoms include fever, chills, malaise, weight loss, abdominal discomfort, and night sweats, but about 50% of patients are asymptomatic.[14]​ Nearly all patients have elevated white blood cell counts and around 75% of patients have splenomegaly.​[14][15]​​​ Diagnosis should be confirmed by the presence of the Philadelphia chromosome and/or the BCR-ABL1 transcripts in peripheral blood or bone marrow cells.[16]​​[17]

Blast crisis refers to the transformation of chronic myeloid leukemia (CML) from the chronic or accelerated phase to the blast phase. The blast phase is confirmed by the percentage of blast cells (≥20% [WHO criteria]) in the peripheral blood or bone marrow, or the presence of an extramedullary accumulation of blast cells, or large foci or clusters of blasts in the bone marrow biopsy.[17][18] Anemia, infections, abnormal/excessive bleeding, bone pain, and constitutional symptoms (night sweats, weight loss, fever, fatigue) are common presenting complaints of blast-phase CML. 

A B-cell malignancy commonly characterized by symptoms of fatigue, a markedly enlarged spleen, and a distinctive histologic appearance (B-cells with delicate cytoplasmic projections resembling hair) on peripheral blood smear and bone marrow biopsy. Hairy cell leukemia (HCL) is relatively uncommon, with marked geographic variation in frequency. The median age at diagnosis is 58 years; HCL affects more men than women.[19][20]​​HCL often presents with abdominal discomfort or fullness. This is attributed to splenomegaly, which is present in around 60% to 70% of patients.[19]​​[21]​ The disease is not curable. However, it is highly responsive to therapy and may be managed successfully for a decade or more.

The causes of pancytopenia are diverse, and likely causes differ in children and adults. Unless the underlying cause is already apparent (and being appropriately managed), the presence of pancytopenia always warrants investigation by a hematologist. Leukemias may cause pancytopenia through decreased production, or increased destruction or sequestration, of blood cells.

Neutrophils are essential components of the hematopoietic and immune system, and quantitative or qualitative abnormalities of neutrophils can result in life-threatening infection. In adults, the most likely causes of neutropenia are infection, drug-induced neutropenia, or primary acquired bone marrow disease. In children <2 years of age, the most likely cause is an immune neutropenia. Leukemias are a cause of acquired neutropenia, accounting for some of the typical symptoms (e.g., recurrent infections).



Editorial Team

BMJ Publishing Group


This overview has been compiled using the information in existing sub-topics.

Use of this content is subject to our disclaimer