eMedicine Specialties > Pediatrics: General Medicine > Oncology
Acute Lymphoblastic Leukemia
Updated: Aug 12, 2009
Introduction
Background
Acute lymphoblastic leukemia (ALL) is the most common malignancy diagnosed in children, representing nearly one third of all pediatric cancers. The annual incidence rate for acute lymphoblastic leukemia is 30.9 cases per million population. The peak incidence occurs in children aged 2-5 years.
Although a few cases are associated with inherited genetic syndromes (ie, Down syndrome, Bloom syndrome, Fanconi anemia), the cause remains largely unknown. Many environmental factors (ie, exposure to ionizing radiation and electromagnetic fields, parental use of alcohol and tobacco) have been investigated as potential risk factors, but none has been definitively shown to cause acute lymphoblastic leukemia. Various viruses may be linked to the development of leukemia, particularly when prenatal viral exposure occurs in mothers recently infected with influenza or varicella. However, no direct link has been established between viral exposure and the development of leukemia.
Acute lymphoblastic leukemia may also occur in children with various congenital immunodeficiencies (ie, Wiskott-Aldrich syndrome, congenital hypogammaglobulinemia, ataxia-telangiectasia) that have an increased predisposition to develop lymphoid malignancies.
With improvements in diagnosis and treatment, overall cure rates for children with acute lymphoblastic leukemia now approach 80%. Further refinements in therapy, including the use of risk-adapted treatment protocols, may improve cure rates for patients at high risk while limiting the toxicity of therapy for patients with a low risk of relapse. This article summarizes advances in the diagnosis and treatment of childhood acute lymphoblastic leukemia.
Pathophysiology
In acute lymphoblastic leukemia, a lymphoid progenitor cell becomes genetically altered and subsequently undergoes dysregulated proliferation, survival, and clonal expansion. In most cases, the pathophysiology of transformed lymphoid cells reflects the altered expression of genes whose products contribute to the normal development of B cells and T cells. Several studies indicate that leukemic stem cells are present in certain types of acute lymphoblastic leukemia.1,2
Frequency
United States
Annually, 2500-3500 children are diagnosed with acute lymphoblastic leukemia.
International
Throughout the world, the incidence rate is thought to be similar to that in the United States.
Mortality/Morbidity
Overall cure rates for children with acute lymphoblastic leukemia now approach 80%. The 4-year event-free survival (EFS) rate for high-risk patients is approximately 65%.
Race
The overall incidence of acute lymphoblastic leukemia varies among different racial groups within the United States. White children are more frequently affected than black children.
Sex
Acute lymphoblastic leukemia occurs slightly more frequently in boys than in girls. This difference is most pronounced for T-cell acute lymphoblastic leukemia.
Age
The incidence of acute lymphoblastic leukemia peaks in children aged 2-5 years.
Clinical
History
Children with acute lymphoblastic leukemia (ALL) generally present with signs and symptoms that reflect bone marrow infiltration and extramedullary disease. Because leukemic blasts replace the bone marrow, patients present with signs of bone marrow failure, including anemia, thrombocytopenia, and neutropenia. Clinical manifestations include fatigue and pallor, petechiae and bleeding, and fever. In addition, leukemic spread may manifest as lymphadenopathy and hepatosplenomegaly. Other signs and symptoms of leukemia include weight loss, bone pain, and dyspnea.
Signs or symptoms of CNS involvement, even when it occurs, are rarely observed at the time of the initial diagnosis. The signs and symptoms include headache, nausea and vomiting, lethargy, irritability, nuchal rigidity, and papilledema. Cranial nerve involvement, which most frequently involves the seventh, third, fourth, and sixth cranial nerves, may occur. Also, leukemia can present as an intracranial or spinal mass, which causes numerous neurologic symptoms, most of which are due to nerve compression.
Testicular involvement at diagnosis is rare. However, if present, it appears as painless testicular enlargement and is most often unilateral.
Physical
Physical findings in children with acute lymphoblastic leukemia reflect bone marrow infiltration and extramedullary disease. Patients present with pallor caused by anemia and petechiae and bruising secondary to thrombocytopenia. They also have signs of infection because of neutropenia. In addition, leukemic spread may be seen as lymphadenopathy and hepatosplenomegaly.
Careful neurologic examination to look for CNS involvement is important because the treatment for leukemia with CNS involvement is different.
In male patients, testicular examination is necessary to look for testicular involvement of leukemia.
Causes
Although a small percentage of cases are associated with inherited genetic syndromes, the cause of acute lymphoblastic leukemia remains largely unknown.
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References
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Further Reading
Keywords
acute lymphocytic leukemia, acute lymphatic leukemia, acute lymphoid leukemia, ALL, pediatric cancer, childhood cancer, childhood malignancy, inherited genetic syndromes, lymphoblastic leukemia, leukemia, leukemic blasts, T cell, T-cell ALL, B cell, B-lineage ALL, BCR-ABL, MLL, high-risk ALL, exposure to ionizing radiation, exposure to electromagnetic fields, allogeneic hematopoietic stem cell transplantation, HSCT, bone marrow failure, anemia, thrombocytopenia, neutropenia, petechiae, bleeding, lymphadenopathy, hepatosplenomegaly, bone pain, Down syndrome, Fanconi anemia, Bloom syndrome, influenza, varicella, Wiskott-Aldrich syndrome, congenitalhypogammaglobulinemia, ataxia-telangiectasia
Overview: Acute Lymphoblastic Leukemia