Definition

The World Health Organisation (WHO) classification system organises haematological malignancies by the cell lineage and the maturity of the diseased cell³:

• Myeloid lineage – neutrophils, eosinophils, basophils, monocytes and platelets
• Lymphoid lineage – B-lymphocytes, T-lymphocytes and NK-cells

Leukaemia is further split into acute and chronic subtypes:

• Acute leukaemias are characterised by problems with cell maturation, causing death within weeks or months if untreated⁴. This is felt to reflect a defect originating close to the haematopoietic stem cell⁵.
• Chronic leukaemias are characterised by problems with proliferation, but cells retain the ability to mature, causing death within months to years if untreated⁴.

Leukaemia refers to the presence of malignant cells in the peripheral blood. Lymphoma refers to the malignant proliferation of lymphocytes; which can present with lymphadenopathy or with diseased cells within the blood (i.e. a leukaemia)⁶. There is therefore considerable overlap between leukaemia and lymphoma, with some specific diseases clinically overlapping between the two. 

This learning session will focus primarily on Acute Myeloid Leukaemia (AML) and Acute Lymphoblastic Leukaemia (ALL). These diseases, or complications related to their treatment, are the most likely to present to an emergency department. Within the context of emergency department management, they are virtually indistinguishable, and will be referred to jointly as acute leukaemia.

Learning bite: Acute leukaemia can cause death within weeks if not recognised and treated.