Leukemia, Acute Lymphoblastic (ALL) in Adults
- Acute lymphoblastic leukemia (ALL) in adults is the result of a clonal proliferation, survival, and impaired differentiation of immature lymphocytes. These early lymphoid cells take the place of normal hematopoietic cells in the bone marrow.
- The World Health Organization (WHO) defines ALL as the presence of ≥25% lymphoblasts in the bone marrow; the US uses ≥20% as the cutoff.
- ALL and lymphoblastic lymphoma (LBL) can arise from the same precursor cell lineage and be considered diseases along the same spectrum:
- LBL presents as a mass, possibly, but not limited to, the mediastinum, with <25% blasts in the bone marrow.
- ALL may present with a mass lesion but contains ≥25% bone marrow involvement.
- Any organ can be affected.
Many chemotherapy (CTX) drugs are teratogenic.
ALL is the most common malignancy in children: accounts for 30% of all pediatric malignancies and 80% of pediatric leukemias (see “Acute Lymphoblastic Leukemia, Pediatric”).
Patients >60 years with ALL have a 42% mortality during induction CTX. The cause of death is usually CTX-related complications or relapse. Survival is often reduced due to poor tolerance of CTX; thus, leading to dose reductions and ineffective medication delivery.
- Incidence of ALL is 1.8/100,000 per year.
- In 2021, 5,690 new cases of ALL in the United States
- Higher incidence in older age, males, whites, those with history of radiation, CTX, or certain genetic disorders
- Prevalence of ALL can range from 15–50% and increases with age.
- Bimodal distribution: early peak in childhood, second peak at around age 50 years.
- 75–80% of cases occur in children, approximately 20% in adults.
Etiology and Pathophysiology
The pathophysiology of ALL involves the abnormal proliferation and differentiation of clonal lymphoid cells. These malignant cells proliferate and replace the bone marrow cells that would normally create red blood cells, neutrophils, and platelets. Therefore, resulting in anemia, neutropenia, and thrombocytopenia.
- Higher rates in monozygotic and dizygotic twins
- Increased risk of ALL with diseases related to chromosomal instability and inherited chromosomal abnormalities
- Age >70 years, radiation and CTX exposure, and infection with HIV are risk factors for developing ALL.
- Human T-cell lymphotropic virus type 1 is associated with adult T-cell ALL.
- Epstein-Barr virus is associated with mature B-cell ALL.
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