Overview
Definition
A malignant neoplasm of the bone marrow in which early lymphoid precursors (lymphoblasts) proliferate and replace normal hematopoietic cells.
Epidemiology
The most common childhood cancer (peak age 2-5 years). Highly curable in children, worse prognosis in adults.
Etiology & Risk Factors
- Genetic mutations in lymphoid precursors. Strongly associated with Down Syndrome (Trisomy 21).
Clinical Symptoms
- Bone pain (due to marrow expansion), causing limp in children
- Fever and frequent infections (neutropenia)
- Pallor and fatigue (anemia)
- Petechiae, purpura, easy bruising, and epistaxis (thrombocytopenia)
- Hepatosplenomegaly and Lymphadenopathy
Clinical Approach
Diagnosis
- CBC: Can show leukocytosis or leukopenia, but reveals Anemia and Thrombocytopenia
- Peripheral Smear: Presence of circulating Lymphoblasts
- Bone Marrow Biopsy (Gold Standard): > 20% Lymphoblasts in the marrow
- Flow Cytometry (Terminal deoxynucleotidyl transferase - TdT positive)
Management
- Multi-agent systemic Chemotherapy (Induction, Consolidation, and prolonged Maintenance phases)
- Intrathecal chemotherapy (Methotrexate) for CNS prophylaxis (ALL frequently hides in the CNS and testes)
- Hematopoietic Stem Cell Transplant (for high-risk or relapsed cases)
Complications
- Tumor Lysis Syndrome (hyperkalemia, hyperphosphatemia, hypocalcemia, hyperuricemia causing renal failure)
- Severe immunocompromise
- Relapse