LeukemiaEdit
Leukemia is a group of cancers that originate in the body's hematopoietic system, typically in the bone marrow, where blood cells are formed. It is characterized by the clonal proliferation of abnormal white blood cells (leukocytes) that crowd normal cells and impair the production of red cells and platelets. Leukemia is not a single disease; it includes several subtypes that differ in cell lineage (lymphoid versus myeloid) and in how rapidly the disease progresses (acute versus chronic). Depending on subtype and patient factors, leukemia presents across a wide age range—from forms that occur predominantly in children to others that are more common in older adults.
Advances in diagnosis and treatment—ranging from targeted therapies and immunotherapies to stem cell transplantation—have improved outcomes for many patients. Management requires a multidisciplinary approach and continues to be shaped by ongoing research and, at times, debates about treatment access and cost. Leukemia sits at the intersection of basic biology, clinical medicine, and public health, with ongoing work aimed at earlier detection, more effective therapies, and better supportive care for those affected.
Overview
Leukemia arises when malignant transformation occurs in hematopoietic stem cells or progenitor cells, leading to uncontrolled production of immature leukocytes that suppress normal hematopoiesis. The disease can involve the blood, bone marrow, and sometimes other organs such as the lymph nodes, spleen, and liver. The two major cellular lineages implicated are lymphoid and myeloid, giving rise to the principal subtypes known as acute lymphoblastic leukemia Acute lymphoblastic leukemia, acute myeloid leukemia Acute myeloid leukemia, chronic lymphocytic leukemia Chronic lymphocytic leukemia, and chronic myeloid leukemia Chronic myeloid leukemia.
Key molecular features influence prognosis and treatment. For example, the presence of the Philadelphia chromosome (a specific genetic abnormality) is a hallmark in certain cases of chronic myeloid leukemia and some acute lymphoblastic leukemia, and it guides the use of targeted therapies such as tyrosine kinase inhibitors Philadelphia chromosome and tyrosine kinase inhibitors. Understanding the genetic and immunophenotypic profile of leukemic cells is essential for selecting therapy, including chemotherapy regimens, targeted agents, and immunotherapies. Leukemia treatment often includes supportive care to manage anemia, bleeding, infection risk, and complications related to treatment itself, with transfusions and growth factors playing supportive roles when needed. See also bone marrow and hematopoietic stem cell biology for foundational context.
Types
Acute lymphoblastic leukemia (ALL)
ALL is the most common form in children but also occurs in adults. It typically requires prompt, intensive chemotherapy and may include central nervous system-directed therapy. In some patients, especially adults or those with specific genetic features, targeted therapies or immunotherapies such as monoclonal antibodies or CAR-T cell therapy may be used. Long-term survival has improved with advances in treatment regimens and supportive care. See Acute lymphoblastic leukemia for more detail.
Acute myeloid leukemia (AML)
AML is more common in adults and is driven by genetic and epigenetic changes in myeloid progenitors. Induction chemotherapy aims to induce remission, followed by consolidation therapy which may include stem cell transplantation in appropriate candidates. Targeted therapies (for example, inhibitors targeting FLT3 or IDH mutations) have expanded options for subsets of patients. See Acute myeloid leukemia for more detail.
Chronic lymphocytic leukemia (CLL)
CLL typically progresses slowly and is often detected incidentally or during evaluation for nonspecific symptoms. Management ranges from active observation in early-stage disease to chemoimmunotherapy or targeted therapies (such as BTK inhibitors) in progressive cases. Allogeneic stem cell transplantation is uncommon in CLL but may be considered in select situations. See Chronic lymphocytic leukemia for more detail.
Chronic myeloid leukemia (CML)
CML is driven by the BCR-ABL fusion gene, most often treated effectively with tyrosine kinase inhibitors that block the abnormal signaling driving the leukemia. With modern therapies, many patients achieve long-term disease control. See Chronic myeloid leukemia for more detail.
Signs and symptoms
Leukemia often presents with symptoms related to insufficient normal blood cell production or systemic effects. Common signs include: - Fatigue and pallor from anemia - Easy bruising or unusual bleeding due to thrombocytopenia - Frequent infections or fever from immune system impairment - Bone or joint pain in some subtypes - Swollen lymph nodes, an enlarged spleen, or liver - Unexplained weight loss or night sweats in some patients
Some symptoms are more characteristic of certain subtypes and age groups. Patients may arrive with signs of acute illness or, in chronic forms, with subtle indicators that lead to gradual diagnosis through routine blood tests. See anemia and thrombocytopenia for related conditions.
Diagnosis
Diagnosis combines laboratory testing, cell analysis, and genetic studies. Typical steps include: - Complete blood count with differential to assess counts of red cells, platelets, and white cells - Peripheral blood smear to examine cell morphology - Bone marrow biopsy and aspiration to evaluate marrow cellularity and lineage - Immunophenotyping by flow cytometry to classify leukemic cells as lymphoid or myeloid - Cytogenetic and molecular testing to identify chromosomal abnormalities and gene mutations (for example, Philadelphia chromosome status, BCR-ABL fusion, FLT3 mutations, NPM1 mutations) - Imaging studies to assess organ involvement and treatment response in some cases
See complete blood count and bone marrow biopsy for foundational diagnostic concepts, and flow cytometry and cytogenetics for techniques used in classification and prognosis.
Treatment
Treatment modalities are tailored to subtype, patient age, performance status, and genetic features. Core approaches include: - Chemotherapy regimens designed for induction (to achieve remission) and consolidation - Targeted therapies that inhibit specific molecular drivers (for example, tyrosine kinase inhibitors for CML and some ALL cases) - Immunotherapies such as monoclonal antibodies and, in certain settings, CAR-T cell therapy for select leukemias - Stem cell transplantation (allogeneic) in appropriate patients or high-risk cases - Supportive care to manage anemia, infections, and bleeding, including transfusions and growth factors
For each major subtype, treatment principles differ: - ALL: aggressive multi-agent chemotherapy, CNS-directed therapy, consideration of transplant in higher-risk cases - AML: induction with cytarabine-containing regimens, possible consolidation and transplant for eligible patients - CLL: risk-adapted therapy ranging from observation to chemoimmunotherapy or targeted agents - CML: continuous therapy with tyrosine kinase inhibitors to control disease, with transplantation as a potential option in resistant cases
See chemotherapy for general principles of cancer treatment, bone marrow transplantation for a key option in eligible patients, and CAR-T cell therapy for a modern immunotherapy approach.
Prognosis
Prognosis varies widely by subtype, age, genetic features, response to initial therapy, and access to advanced treatments. Some forms in children have high cure rates with modern regimens, while certain adult forms may require ongoing management. Prognostic tools integrate clinical factors with genetic and molecular markers to guide treatment decisions. See prognosis and the specific subtype pages for detailed information.
History
The study of leukemia advanced rapidly through the 20th century, with improvements in diagnostic techniques and the development of multi-agent chemotherapy. The identification of the Philadelphia chromosome and subsequent entry of targeted therapies transformed outcomes for many patients with CML and related leukemias. Bone marrow transplantation emerged as a life-saving option for a subset of patients and has continued to evolve with better donor matching and conditioning regimens. See also history of medicine and bone marrow transplantation for broader context.