Leukemia is a type of cancer that originates in the blood-forming tissues, primarily within the bone marrow, the spongy material inside bones. In a healthy body, stem cells in the bone marrow develop into various blood components, including red blood cells, white blood cells, and platelets. Leukemia occurs when these blood-forming cells undergo changes, becoming abnormal leukemia cells that multiply excessively and can interfere with the production and function of healthy blood cells. This condition can affect individuals across the entire lifespan, from infancy through older adulthood.
Leukemia Across All Ages
While leukemia can manifest at any point in life, its incidence and the specific types encountered vary considerably across different age groups. The patterns of leukemia diagnosis are not uniform; instead, distinct forms of the disease tend to be more prevalent during certain periods of life. This age-related variability means that the type of leukemia diagnosed in a young child often differs from that found in a middle-aged adult or an older individual.
Childhood Onset Leukemia
Leukemia is the most common cancer diagnosed in children and adolescents under 20, accounting for over a quarter of all cancer cases in this age group. Acute lymphoblastic leukemia (ALL) is the predominant type, representing about 75% of childhood leukemias. ALL most frequently occurs in early childhood, typically peaking between ages 2 and 5.
Acute myeloid leukemia (AML) is the second most common type of childhood leukemia, making up 15% to 20% of cases. AML is more likely to be diagnosed in the first year of life and during the teenage years. Chronic leukemias, such as chronic myeloid leukemia (CML) and juvenile myelomonocytic leukemia (JMML), are rare in children, though CML is occasionally seen in teenagers and JMML usually occurs around age 2.
Adult Onset Leukemia
Acute myeloid leukemia (AML) is the most frequently diagnosed acute leukemia in adults. While AML can occur at any age, its prevalence increases after age 45.
Chronic lymphocytic leukemia (CLL) is the most common type of chronic leukemia in adults. CLL typically affects individuals aged 30 and older.
Chronic myeloid leukemia (CML) primarily affects adults, with a median age of diagnosis around 65. CML symptoms may not appear for months or years due to its slow progression.
Older Adult Onset Leukemia
Leukemia incidence increases with advancing age. Adults between 65 and 74 have the highest risk of developing leukemia.
Chronic lymphocytic leukemia (CLL) is the most common type among older adults, with the median age of diagnosis being around 71 or 72 years. About 70% of CLL patients are diagnosed after age 65, and 40% are diagnosed at age 75 or older.
Acute myeloid leukemia (AML) is also common in older adults, with a median age of diagnosis around 68 years. Genetic mutations that accumulate over time are thought to contribute to the increased incidence of AML in older individuals. Myelodysplastic syndromes (MDS), a group of conditions where blood cells in the bone marrow do not mature properly, can sometimes progress to AML in older patients.