Overview
Leukaemia is cancer of the blood and bone marrow, characterised by uncontrolled production of abnormal white blood cells that crowd out normal blood cells. The four main types are acute lymphoblastic (ALL), acute myeloid (AML), chronic lymphocytic (CLL), and chronic myeloid (CML). Treatment and prognosis vary markedly by type and age.
How common is it?
Leukaemia affects children and adults, but the pattern differs by subtype. ALL is the most common leukaemia in children; CLL mainly affects older adults.
Causes and risk factors
Leukaemia results from acquired or inherited genetic mutations that cause abnormal proliferation and arrested maturation of haematopoietic cells.
Common risk factors
- Previous radiation or chemotherapy exposure
- Benzene exposure
- Genetic syndromes including Down syndrome, Fanconi anaemia and ataxia-telangiectasia
- Chromosomal abnormalities: Philadelphia chromosome t(9;22) in CML and ALL
- HTLV-1 infection can cause adult T-cell leukaemia/lymphoma; most leukaemias are not caused by a known infection.
- Smoking (increases AML risk)
- Inherited predisposition (rare familial leukaemia syndromes)
- Age: CLL almost exclusively in older adults
Symptoms
- Fatigue and breathlessness (anaemia from bone marrow failure)
- Increased bleeding and bruising (thrombocytopenia)
- Recurrent or severe infections (neutropenia)
- Fever, night sweats
- Unexplained weight loss
- Bone and joint pain (particularly in ALL in children)
- Swollen lymph nodes and spleen (CLL/CML)
- Pale skin
When to see a doctor
Seek urgent GP assessment for unexplained bruising, persistent infections, fever without obvious cause, or significant fatigue. These require a full blood count urgently.
Diagnosis
Full blood count and blood film: abnormal white cells and reduced normal cell lines. Bone marrow aspirate and trephine biopsy confirms diagnosis and type. Cytogenetics and molecular testing (e.g. BCR-ABL for CML) guides treatment. Immunophenotyping by flow cytometry.
Treatments
Chemotherapy
Combination chemotherapy is important in ALL and AML. Treatment phases depend on the subtype; prolonged maintenance is usual in ALL but not universal in AML. Targeted medicines may also be used.
Targeted therapy
Tyrosine kinase inhibitors such as imatinib and dasatinib target BCR-ABL in CML. They allow many people to control the disease for years, with regular blood tests and specialist follow-up.
Allogeneic stem cell transplant
Potentially curative for AML and ALL by replacing the bone marrow with donor cells that provide both new haematopoiesis and graft-versus-leukaemia effect. Reserved for high-risk disease.
Watchful waiting (CLL)
Many people with early CLL have active monitoring rather than immediate treatment. When needed, targeted medicines are usually the main treatment; chemotherapy is used less often. Decisions depend on symptoms, progression and general health.
Self-care and lifestyle
- Avoid infection vigilantly during intensive chemotherapy (high infection risk)
- Ensure vaccinations are up to date before starting immunosuppressive treatment
- Bone marrow or stem cell donation is desperately needed from diverse ethnic backgrounds
- Maintain nutrition during treatment to support recovery
Prevention
Most leukaemia is not preventable. Avoiding smoking reduces AML risk. Occupational benzene exposure is regulated. Early genetic counselling for known familial risk.
Sources for targeted updates
Updated: 24 October 2026. Specific treatment, safety or key-fact statements corrected in this update; further corrections to frequency. This update covers the named sections; a full review of the remaining guide is pending.