Leukaemia in the young child.

Leukaemia is rare in infancy with an equal predominance of lymphoblastic and myeloblastic cases. Acute lymphoblastic leukaemia in infants under one year is characterised by a high leucocyte count, organomegaly, early B-cell phenotype, sometimes with evidence of monocytoid differentiation and cytogenetic abnormalities. This is reflected in its poor prognosis. The toddler (aged 1-2) tends to develop typical childhood ALL which is responsive to treatment, but remains vulnerable to late effects of therapy, particularly radiation. The distribution of subtypes of AML differs in the younger and older child and results of treatment have improved in all age groups. A uniform strategy appears desirable for all cases of childhood AML. It seems probable that different genetic and environmental factors may be involved in the genesis of infant ALL, childhood ALL and AML in children. The management of leukaemia in children under two poses a considerable challenge.