Overview & Definition

Leukemia is a cancer of the blood-forming tissues—primarily bone marrow and blood—where abnormal white blood cells grow uncontrollably, crowding out healthy cells and causing infection risk, anemia, and bleeding problems. Leukemias are classified by speed (acute vs chronic) and cell lineage (lymphoid vs myeloid).

Major Types

• ALL — acute lymphoblastic leukemia
• AML — acute myeloid leukemia
• CLL — chronic lymphocytic leukemia
• CML — chronic myeloid leukemia (BCR-ABL1–driven)
• Other less common leukemias (e.g., hairy cell leukemia)

Risk Factors

• Age/sex patterns (varies by type)
• Genetic factors (e.g., Down syndrome)
• Prior chemo/radiation; benzene exposure
• Preexisting marrow disorders (e.g., MDS → AML)

Many people have no identifiable risk factor.

Signs & Symptoms

• Fatigue, shortness of breath (anemia)
• Frequent infections, fevers, night sweats
• Easy bruising/bleeding, petechiae
• Bone pain, swollen nodes, enlarged spleen
• Unintended weight loss

Diagnosis & Classification

Treatment Options

• Chemotherapy (multi-phase for acute leukemias)
• Targeted therapy (TKIs for CML/Ph+ ALL; FLT3/IDH inhibitors for AML; BTK/BCL2 inhibitors for CLL)
• Immunotherapy (monoclonal/bispecific antibodies, CAR T cells in select settings)
• Stem cell transplant for selected high-risk/relapsed cases
• Supportive care (transfusions, antimicrobials, growth factors)

Prognosis

Varies by type and genetics. Many children with ALL are cured; chronic leukemias can be controlled for years; some high-risk acute leukemias require intensive treatment and transplant.

Sources & Attribution

• NCI — Leukemia: cancer.gov/types/leukemia
• CDC — Leukemia Basics: cdc.gov/cancer/leukemia
• MedlinePlus — Leukemia: medlineplus.gov/leukemia.html

Educational only; not medical advice.