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About 3,000 children in the United States and 5,000 children in Europe are diagnosed with ALL per year.

The peak incidence occurs between 2 and 5 years of age. ALL may be either asymptomatic or acute with a life-threatening haemorrhage, infection, or episode of respiratory distress. Although ALL primarily affects the bone marrow and peripheral blood, any organ or tissue may be infiltrated by the abnormal cells. The most frequent signs are lymphadenopathies, hepatosplenomegaly, fever, signs of haemorrhage, and bone pain.

Most cases show chromosomal and genetic abnormalities, occurring spontaneously in genes playing important regulatory roles in controlling the lymphoid cell population. The most common ALL translocation, the t(12;21), appears to have good prognostic implications.

ALL is biologically heterogeneous and morphologic, immunologic, cytogenetic, biochemical, and molecular genetic characterisation of leukaemia lymphoblasts is needed to establish the diagnosis or to exclude other possible causes of bone marrow failure and, finally, to classify ALL subtypes. Biological findings include hyperleukocytosis due to circulating lymphoblasts, anaemia and thrombocytopaenia. Diagnosis is established by bone marrow biopsy revealing leukaemic cell infiltration.

The chemotherapy protocols adopted by international cooperative groups have four main objectives: induction with the aim of complete remission, preventative therapy to avoid central nervous system involvement, consolidation/re-induction, and maintenance therapy. Although management of relapse remains largely controversial, high dose chemotherapy blocks and stem cell transplantation are approaches increasingly adopted in most cases. In 2006, clofarabine obtained EU marketing authorisation as an Orphan drug for second line treatment of paediatric ALL patients. A novel tyrosine-kinase inhibitor, dasatinib, has been shown to be a safe and effective treatment option for adults with Philadelphia chromosome-positive acute lymphoblastic leukaemia and resistance or intolerance to imatinib. Clinical trials with this inhibitor are ongoing in the paediatric population. With the need to stratify patients into risk groups and to provide risk-adapted therapy, treatment requires high levels of organisation, expertise and knowledge.

The increase in the survival rate for children younger than 15 years of age has been dramatic, moving from less than 10% in the early 60's to about 75% in the late 90's. Unfortunately, however, results are still rather poor in countries with limited resources, which are home to around 80% of the child population.