PA18.1-2 | Acute Leukaemias — AML & ALL — Summary & Reflection

REFLECT

Consider the 6-year-old in the opening case. You now have the framework to approach his diagnosis. Walk through it: (1) What does his CBC pattern tell you? (2) What lineage would you predict from his age, lymphadenopathy, hepatosplenomegaly, and bone pain? (3) What cytochemical stains and flow markers would you order first? (4) If his cytogenetics show ETV6-RUNX1 fusion, how does his prognosis change compared to an adult with t(9;22)? (5) What complication would you watch for in the first 48 hours after starting chemotherapy?

Jot down your answers before checking the summary — this self-test reveals whether you can apply the framework, not just recall facts.

KEY TAKEAWAYS

Core take-aways for acute leukaemias:

1. Definition and threshold: Leukaemia = clonal haematopoietic malignancy. Acute = ≥20% blasts (WHO) with rapid course. Chronic = <20% blasts, indolent course.

1. Aetiology: Radiation, benzene, alkylating chemo agents, prior MDS, Down syndrome, DNA repair defect syndromes.

1. Pathogenesis: Maturation arrest (Class II hit) + clonal proliferation (Class I hit) → marrow failure.

1. AML vs ALL — key distinguishers:

5. Must-know cytogenetics:
- APL t(15;17) → PML-RARα → DIC → ATRA curative
- t(8;21) and inv(16) → favourable AML
- Hyperdiploidy and ETV6-RUNX1 → favourable ALL
- Ph+ t(9;22) in ALL → poor without TKI

1. Clinical features: Anaemia + infections + bleeding (marrow failure) PLUS organomegaly, lymphadenopathy, bone pain, CNS involvement in ALL; gum hypertrophy in monocytic AML.

1. Diagnosis: BM ≥20% blasts + morphology + cytochemistry + flow immunophenotyping + cytogenetics.

1. TLS: Hyperkalaemia + hyperphosphataemia + hyperuricaemia + AKI — prevent with hydration + allopurinol/rasburicase.