Leukemia is a progressive, malignant disease of the blood-forming organs, characterized by distorted proliferation and development of leukocytes and their precursors in the blood and bone marrow. It can be classified as acute or chronic, according to the degree of cell differentiation (not the duration of disease), and as myelogenous or lymphocytic, according to the predominant type of cell involved (myeloid or lymphoid). Several subtypes have been identified. The exact cause of leukemia is unknown, but genetic and environmental risk factors have been identified for many subtypes. Typical signs and symptoms might include fatigue, weight loss, fever, pallor, ecchymoses, petechiae, dyspnea, dizziness, palpitations, bleeding, and recurrent infections, although each subtype has its distinguishing features. Definitive diagnoses often require bone marrow biopsy and/or blood analysis.
A malignant clonal disease that develops when a B/T-precursor-stage lymphoid progenitor cell becomes genetically altered through somatic changes and undergoes uncontrolled proliferation. This progressive clonal expansion eventually leads to acute lymphocytic 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 is most commonly diagnosed in those ages under 20 years. It accounts for 80% of leukemias in pediatric patients and 20% in adults. Clinical presentation is heterogenous and reflects the biological subtype. Most patients present with signs and symptoms associated with cytopenias. Enlarged lymph nodes are also frequently the initial prompt for the patient to seek medical attention. T-lineage ALL is characterized by an older age of onset, male gender preponderance, and inferior outcome in comparison with B-ALL. The cytogenetic abnormality has prognostic implications.
A cancer of B lymphocytes. Failure of B lymphocytes to undergo maturation and full differentiation leads to a monoclonal population of dysfunctional but self-renewing B lymphocytes. These lymphocytes can infiltrate lymphatic tissues and hematopoietic organs such as the liver, spleen, and bone marrow. A key risk factor is age over 60 years. Lymphadenopathy, splenomegaly (in 50% of cases), shortness of breath and fatigue are key diagnostic factors. It is diagnosed by complete blood count (CBC) with differential, blood smear showing smudge cells, and flow cytometry. Most patients are diagnosed following a routine CBC for an unrelated reason.
The clonal expansion of myeloid blasts in the bone marrow, peripheral blood or extramedullary tissues. Occurs predominantly in older adults. Common findings are pallor, ecchymoses and petechiae. Management of acute promyelocytic leukemia (APML), an aggressive subtype of acute myelogenous leukemia (AML) with distinct cytologic and clinical features, is distinct from that of standard AML treatment.
A malignant clonal disorder of the hematopoietic stem cell that results in marked myeloid hyperplasia of the bone marrow. Incidence peaks between the ages of 65 and 74 years, median age at diagnosis is 65 years. The only known risk is exposure to ionizing radiation. Possible symptoms include fever, chills, malaise, weight loss, abdominal discomfort, and night sweats, but approximately one third of patients are asymptomatic. Nearly all patients have elevated white blood cell counts and around 75% of patients have splenomegaly. Diagnosis should be confirmed by the presence of the Philadelphia chromosome and/or the BCR-ABL1 transcripts in peripheral blood or bone marrow cells.
Blast crisis refers to the transformation of chronic myelogenous leukemia (CML) from the chronic or accelerated phase to the blast phase. The blast phase is defined as the presence of ≥30% myeloblasts in the blood, bone marrow, or both, or the presence of extramedullary disease (International Bone Marrow Transplant Registry criteria). Anemia, infections, abnormal bleeding, bone pain, and constitutional symptoms (night sweats, weight loss, fever, fatigue) are common presenting complaints of blast-phase CML. The treatment goal is to achieve a complete hematologic remission or at least return to the chronic phase in order to perform stem cell transplant.
A B-cell malignancy commonly characterized by symptoms of fatigue, a markedly enlarged spleen, and a distinctive histologic appearance on peripheral blood smear (B-cells with delicate cytoplasmic projections resembling hair) and bone marrow biopsy. Hairy cell leukemia (HCL) is relatively uncommon, with marked geographic variation in frequency. The median age at occurence is 50 years; HCL affects more men than women. It often presents with abdominal discomfort or fullness. This is attributed to splenomegaly, which is present in around 60% to 90% of patients. The disease is not curable. However, it is highly responsive to therapy and may be managed successfully for a decade or more.
Leukemias may cause pancytopenia through decreased production, or increased destruction or sequestration, of blood cells.
Leukemias are a cause of acquired neutropenia, accounting for some of the typical symptoms e.g., recurrent infections.
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This overview has been compiled using the information in existing sub-topics.
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