Introduction
Leukaemia is the commonest cancer of childhood (about a third of all cases). A clone of immature white cells (blasts) fills the bone marrow, crowds out normal blood production and spreads to other organs. Acute lymphoblastic leukaemia (ALL) makes up about 75–80% (peak at 2–5 years), acute myeloid leukaemia (AML) about 15–20%; chronic myeloid leukaemia and juvenile myelomonocytic leukaemia are rare.
Risk factors
Most children have none. Known: Down syndrome (10–20 times the risk; also transient abnormal myelopoiesis in newborns), neurofibromatosis type 1, Li–Fraumeni syndrome, Fanconi anaemia, ataxia telangiectasia, Bloom syndrome, ionising radiation, previous chemotherapy.
How it presents
Do not give steroids for “arthritis” or unexplained symptoms before a blood count and film: they can mask leukaemia and make it harder to treat.
Investigations
- Full blood count and film: anaemia, low platelets, white count low, normal or very high, blasts on the film.
- Bone marrow aspirate and biopsy: over 20–25% blasts.
- Immunophenotyping (flow cytometry): B- or T-ALL, AML.
- Cytogenetics and molecular tests for risk group (below).
- Lumbar puncture for CNS disease; chest X-ray (mediastinum); urate, potassium, phosphate, calcium, LDH, creatinine (tumour lysis); clotting.