Overview of leukemia

Related Diseases & Conditions

• Acute lymphoblastic leukemia

  Summary

  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 one-half of all cases (53.5%) are diagnosed in those ages under 20 years.[4] ALL represents approximately 11% of new leukemia diagnoses and 0.3% of all new cancer cases in the US.​​[4]​​[5]​​​ There are two forms of ALL: B-ALL (arising from B lymphoid progenitors), and T-ALL (arising from T lymphoid progenitors). 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.
• Chronic lymphocytic leukemia

  Summary

  An indolent lymphoproliferative disorder in which monoclonal B lymphocytes (>5000 cells/microliter [>5 x 10⁹/L]) are predominantly found in peripheral blood.[6] These lymphocytes can infiltrate the lymphatic system and hematopoietic organs such as the liver, spleen, and bone marrow. Chronic lymphocytic leukemia (CLL) is the most common leukemia in the western world.[7] [8]​ It represents 1% of all new cancer cases, and is most frequently diagnosed among people ages 65 to 74 years, in the US.[9]​ Lymphadenopathy, splenomegaly, shortness of breath and fatigue are key diagnostic factors.[10]​​​​​ Patients may present with absolute lymphocytosis as an incidental finding on routine complete blood count (CBC). CLL is diagnosed by CBC with differential, blood smear showing smudge cells, and flow cytometry.​​[10]​​​​​​​
• Acute myeloid leukemia

  Summary

  A hematologic malignancy caused by the clonal expansion of myeloid blasts in the bone marrow, peripheral blood or extramedullary tissues. Occurs predominantly in older adults.[11] In the US, approximately 60% of cases were diagnosed in people ages 65 years or over between 2016 and 2020.[11]​ The exact underlying cause of acute myeloid leukemia (AML) is unknown. However, a number of risk factors have been identified. These include exposure to radiation, benzene, or alkylating agents. Common findings are pallor, ecchymoses and petechiae. AML is a highly heterogeneous disease and many subtypes exist; acute promyelocytic leukemia may be associated with life-threatening coagulopathy.
• Chronic myeloid leukemia

  Summary

  A malignant clonal disorder of the hematopoietic stem cell that results in marked myeloid hyperplasia of the bone marrow.[12] Incidence peaks between the ages of 65 and 74 years, but people of all ages can be affected.[13] Exposure to ionizing radiation is associated with increased risk for chronic myeloid leukemia.[14] Possible symptoms include fever, chills, malaise, weight loss, abdominal discomfort, and night sweats, but about 50% of patients are asymptomatic.[15]​ Nearly all patients have elevated white blood cell counts and around 75% of patients have splenomegaly.​[15] [16]​​​​ All patients require bone marrow biopsy at diagnosis to confirm the phase of disease and for karyotype analysis.
• Blast crisis

  Summary

  Blast crisis refers to the transformation of chronic myeloid leukemia (CML) from the chronic or accelerated phase to the blast phase. Diagnosis is confirmed by the percentage of blast cells (≥20% [WHO criteria] or ≥30% [MD Anderson Cancer Center and the International Bone Marrow Transplant Registry 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]​​ Generally the disease is diagnosed in its chronic form (as opposed to its accelerated or blast forms), which if untreated will progress to fatal blastic disease within 3 to 5 years.[19]​​[20]​ Anemia, infections, abnormal/excessive bleeding, bone pain, or constitutional symptoms (night sweats, weight loss, fever) are common presenting complaints of blast-phase CML.
• Hairy cell leukemia

  Summary

  An indolent mature B-cell neoplasm. It is considered to be a type of non-Hodgkin lymphoma. Seen under the microscope, the leukemic cells have delicate cytoplasmic projections resembling hair ("hairy cells"). Hairy cell leukemia (HCL) is commonly characterized by symptoms of fatigue, a markedly enlarged spleen, and pancytopenia. HCL is relatively uncommon, with marked geographic variation in frequency. The median age at diagnosis has variously been reported between 55 to 59 years. HCL affects more men than women.[21] [22] [23] [24]​ ​​​HCL often presents with abdominal discomfort or fullness. This is attributed to splenomegaly, the most common physical finding, present in over 60% of patients.[21]​​[25] [26]​ HCL is not curable. However, it is highly responsive to therapy; median relapse-free survival of a decade or more has been reported.[24]
• Evaluation of pancytopenia

  Summary

  The causes of pancytopenia are diverse, and causes likely 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.
• Evaluation of neutropenia

  Summary

  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).