Acute leukaemia

What it is

Blasts are immature, undifferentiated precursors, associated with acute leukemia, myelodysplastic syndrome and use of G-CSF, the growth factor that stimulates neutrophil production. When blasts make up more than 20% of the total white cell differential, this is acute leukemia, a medical emergency. A smear in which blasts predominate, without further differentiated precursors or mature neutrophils, suggests a clonal cell disorder, myelodysplastic syndrome or acute leukemia.

Causes and risk

Other marrow disorders may end in acute leukemia. Myelodysplastic syndrome is a hematopoietic stem cell neoplasm whose risk rises with older age and previous chemotherapy or radiation, and it may transform to acute leukemia. In chronic myeloid leukemia (CML) the chronic phase, where 85% are diagnosed, carries few blasts, under 2% in the film and under 5% in the marrow, with slightly elevated eosinophils and basophils, which are the two most important cells in CML; the accelerated phase carries impaired neutrophil differentiation, blasts of 10% to 19%, thrombocytopenia below 100 or thrombocytosis above 1000, and cytogenetic evidence of clonal evolution; and in the blast phase the blasts fail to differentiate, blasts above 20% in blood or marrow being reflective of acute leukemia (1/3 ALL, 2/3 AML).