Childhood Leukemia
Summary of Key Points
Incidence
• Leukemia is the most common childhood cancer.
• The most common subtype, acute lymphoblastic leukemia (ALL), accounts for 75% to 80% of all cases of childhood leukemia, whereas acute myeloid leukemia (AML) comprises approximately 20%.
• Chronic myelogenous leukemia (CML), myelodysplastic syndrome (MDS), and myeloproliferative disorder (MPD) are less frequent.
Epidemiology
• Males are generally affected by leukemia slightly more often than females in all age groups except infants.
• In developed countries, the incidence of ALL is highest between ages 2 and 5 years.
• The incidence of AML is relatively constant during childhood, with slight peaks in the first 2 years of life and in late adolescence.
• MDS typically occurs after 5 years of age and juvenile myelomonocytic leukemia (JMML) occurs nearly always before 5 year of age.
Clinical Findings
• Physical signs and symptoms of thrombocytopenia and anemia are common.
• Neutropenia may lead to severe infection.
• Bone pain and arthralgia caused by leukemic infiltration is more common in ALL than AML and may be especially severe in young children.
• Common sites of extramedullary involvement in ALL include liver, spleen, thymus, and lymph nodes.
• Skin, gums, and the head and neck area are typical sites of extramedullary disease in AML Infiltration of the central nervous system can be found in both ALL and AML.
Differential Diagnosis
• The acute onset of petechiae, ecchymoses, and bleeding may suggest idiopathic thrombocytopenic purpura.
• Both acute leukemia and aplastic anemia may present with pancytopenia and complications associated with bone marrow failure.
• Infectious mononucleosis and other viral infections can be confused with ALL.
• Bone pain, arthralgia, and occasionally arthritis may mimic juvenile rheumatoid arthritis, rheumatic fever, other collagen diseases, or osteomyelitis.
• Childhood ALL should also be distinguished from pediatric small round cell tumors that involve the bone marrow.