Updated: 6/2/2021

Acute Lymphoblastic Leukemia (ALL)

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Snapshot
  • A 7-year-old boy presents with low-grade fever and fatigue. He is notably pale. On physical exam, he has bilateral cervical lymphadenopathy and a mediastinal mass. Blood smear shows increased lymphoblasts. He is referred for a bone marrow biopsy.
Introduction

  • Acute leukemia of lymphoid precursor cells that occurs in children
  • Subtypes
    • B-cell ALL – 85% of all ALL
      • t(12;21) most common in children
      • t(9;22) most common in adults
        • same translocation seen in CML
      • CD10+ and CD19/20+
      • TdT+ (marker of precursor T- and B-cells)
    • T-cell ALL
      • presents in teenagers
      • CD2-8+ (especially CD3+)
      • TdT+ (marker of precursor T- and B-cells)
      • most common presentation is mediastinal mass 
        • infiltration of thymus
  • Epidemiology 
    • < 15 years
    • most common type of cancer and leukemia in children 
    • most cases with no identifiable risk factor
  • Associated conditions
    • Down syndrome in children > 5 years
      • leukemia in Down syndrome children < 5 years = AML
Presentation
  • Symptoms 
    • most common symptom is fever
    • acute onset
      • recurrent infections
      • bleeding
      • fatigue
  • Physical exam
    • mediastinal mass from infiltration of thymus
    • hepatosplenomegaly
    • lymphadenopathy   
Evaluation
  • Best initial test - peripheral blood smear
    • lymphoblasts
  • Most accurate test
    • bone marrow biopsy with cytogenetics
      • ↑ lymphoblasts (> 25%)
      • TdT+, a marker of pre-T and pre-B cells
      • T-cell ALL
        • CD3+
      • B-cell ALL
        • CD10+
        • CD19+
      • negative MPO (myeloperoxidase)
  • CBC reflects bone marrow crowding by neoplasm
    • anemia
    • thrombocytopenia
    • ↓ mature WBCs
Differential Diagnosis
  • AML
  • B-cell lymphoma
  • Non-Hodgkin lymphoma
Treatment
  • Chemotherapy
  • Prophylaxis to CNS (standard chemotherapy does not penetrate blood-brain barrier)
    • intrathecal chemotherapy
Prognosis, Prevention, and Complications
  • Prognosis
    • very responsive to therapy
    • good prognosis in t(12;21)
    • worse prognosis in t(9;22)
  • Complications
    • likes to spread to CNS and testes
    • DIC
    • tumor lysis syndrome 
      • rapid breakdown and turnover of lysed cells causes
        • hyperuricemia
        • hyperkalemia
        • hypocalcemia (most common electrolyte abnormality)

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(M2.ON.15.4679) A 7-year-old boy is brought to his pediatrician by his mother for recent fatigue and intermittent fevers over the past month. She also reports that her son has appeared much paler recently. Vital signs at today's visit are within normal limits. Physical examination is significant for pallor, petechiae, lymphadenopathy, and hepatosplenomegaly. A complete blood count reveals anemia, thrombocytopenia, and neutropenia. A peripheral blood smear is shown in Figure A. Bone marrow aspiration reveals 47% lymphoblasts. Which of the following is associated with this patient's presenting condition?

QID: 107285
FIGURES:
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Klinefelter syndrome

5%

(1/20)

2

Turner syndrome

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(0/20)

3

Down syndrome

90%

(18/20)

4

Edwards syndrome

0%

(0/20)

5

Patau syndrome

0%

(0/20)

M 6 D

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