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Acute Lymphoblastic Leukemia (ALL)

Acute Lymphoblastic Leukemia (ALL) is an aggressive hematologic malignancy caused by uncontrolled proliferation of immature lymphoid precursor cells (lymphoblasts) in the bone marrow. It is the most common childhood cancer but can also occur in adults

Also called

Acute Lymphoid Leukemia

ICD-10

C91.0

Specialty

Hematology

Onset

Acute

Reviewed

August 2026

On This Page

Overview

Acute Lymphoblastic Leukemia (ALL) results from malignant transformation of immature B-cell or T-cell lymphoid precursors. The abnormal lymphoblasts rapidly accumulate in the bone marrow and suppress normal hematopoiesis, causing anemia, thrombocytopenia, and neutropenia. ALL can also infiltrate the CNS, lymph nodes, spleen, liver, and testes.

Etiology & Risk Factors

-Etiology

The exact cause is usually unknown. Acute Lymphoblastic Leukemia (ALL) develops through acquired genetic abnormalities that cause uncontrolled proliferation and impaired differentiation of lymphoid precursor cells.

-Risk Factors

  • Childhood age

  • Previous chemotherapy or radiotherapy

  • Ionizing radiation

  • Genetic syndromes, especially:

    • Down syndrome

    • Li-Fraumeni syndrome

    • Neurofibromatosis type 1

    • Ataxia-telangiectasia

  • Previous hematologic disorders

Pathophysiology

Genetic abnormalities in lymphoid precursor cells → uncontrolled proliferation of immature lymphoblasts → accumulation of lymphoblasts in bone marrow → suppression of normal erythropoiesis, granulopoiesis, and megakaryopoiesis → anemia, neutropenia, and thrombocytopenia → infiltration of lymphoblasts into lymph nodes, liver, spleen, CNS, and other tissues.

Clinical Presentation

Symptoms

  • Fatigue

  • Pallor

  • Fever

  • Recurrent infections

  • Easy bruising

  • Bleeding

  • Bone or joint pain

  • Weight loss

  • Loss of appetite

  • Headache

  • Vomiting

  • Abdominal fullness

Signs

  • Pallor

  • Fever

  • Petechiae

  • Ecchymoses

  • Lymphadenopathy

  • Hepatomegaly

  • Splenomegaly

  • Bone tenderness

  • CNS abnormalities

  • Testicular enlargement in some cases

History Taking

-Ask about:

  • Fatigue
  • Fever
  • Recurrent infections
  • Bleeding
  • Easy bruising
  • Bone or joint pain
  • Weight loss
  • Night sweats
  • Headache
  • Vomiting
  • Neurological symptoms
  • Abdominal fullness
  • Testicular symptoms
  • Previous chemotherapy/radiotherapy
  • Family history
  • Genetic syndromes

Physical Examination

-General Examination

Look for:

  • Pallor

  • Fever

  • Weight loss

  • Petechiae

  • Ecchymoses

Lymph Node Examination

Assess for:

  • Cervical lymphadenopathy

  • Axillary lymphadenopathy

  • Inguinal lymphadenopathy

-Abdominal Examination

Look for:

  • Hepatomegaly

  • Splenomegaly

-Musculoskeletal Examination

Assess for:

  • Bone tenderness

  • Joint tenderness

  • Reduced mobility

-Neurological Examination

Look for:

  • Cranial nerve abnormalities

  • Headache

  • Focal neurological deficits

  • Signs of raised intracranial pressure

Investigations

-Complete Blood Count (CBC)

May show:

  • Anemia

  • Thrombocytopenia

  • Neutropenia

  • Leukocytosis, normal WBC, or leukopenia

  • Circulating lymphoblasts

-Peripheral Blood Film

May show:

  • Lymphoblasts

  • Anemia

  • Thrombocytopenia

  • Abnormal white cell count

-Bone Marrow Aspiration and Biopsy — Gold Standard

Typical findings:

  • Increased lymphoblasts

  • ≥20% lymphoblasts in the bone marrow supports the diagnosis of acute leukemia

-Flow Cytometry

Used to determine lineage:

B-cell ALL

Common markers:

  • CD19

  • CD20

  • CD22

  • CD79a

  • CD10

  • TdT

T-cell ALL

Common markers:

  • CD2

  • CD3

  • CD5

  • CD7

  • TdT

Cytogenetic & Molecular Testing

Important abnormalities include:

  • BCR-ABL1 (Philadelphia chromosome)

  • ETV6-RUNX1

  • KMT2A rearrangement

  • Hyperdiploidy

  • Hypodiploidy

These abnormalities have important prognostic and therapeutic implications.

CNS Evaluation

  • Lumbar puncture with cerebrospinal fluid examination

  • Usually performed as part of staging and treatment planning

Additional Investigations

  • Urea and electrolytes

  • Creatinine

  • Liver function tests

  • LDH

  • Uric acid

  • Coagulation profile

  • Blood group and crossmatch

  • Baseline cardiac assessment before anthracyclines

  • Infection screening before chemotherapy

Diagnosis

Diagnosis is based on:

  • CBC and peripheral blood findings
  • Bone marrow examination
  • Increased lymphoblasts
  • Flow cytometry confirming lymphoid lineage
  • Cytogenetic and molecular testing

Further classification determines:

  • B-cell ALL
  • T-cell ALL
  • Genetic/molecular subtype
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Management

Acute Lymphoblastic Leukemia (ALL) requires multi-phase combination chemotherapy.

  1. Induction

Goal:

Achieve complete remission

Common agents include:

Vincristine
Corticosteroid
Anthracycline
Asparaginase

Additional agents are used according to risk group and protocol.

  1. Consolidation / Intensification

Goal:

Eliminate residual leukemic cells and Reduce relapse risk

Multiple chemotherapy agents are used according to the treatment protocol.

  1. Maintenance

Usually prolonged therapy with:

6-mercaptopurine
Methotrexate
CNS-Directed Therapy

Because the CNS can act as a sanctuary site:

Intrathecal chemotherapy is essential
Methotrexate ± cytarabine depending on protocol
Cranial radiotherapy is reserved for selected high-risk situations

Relapsed / Refractory ALL

Options include:

  • Salvage chemotherapy

  • Blinatumomab

  • Inotuzumab ozogamicin

  • CAR T-cell therapy in selected B-cell ALL

  • Allogeneic hematopoietic stem cell transplantation

Supportive Care

  • Infection prevention and treatment

  • Blood and platelet transfusions

  • Tumor lysis syndrome prophylaxis

  • Antiemetics

  • Fertility preservation when appropriate

  • Nutritional support

Complications

  • Severe anemia
  • Severe infections
  • Bleeding
  • Tumor lysis syndrome
  • CNS involvement
  • Testicular involvement
  • Treatment-related toxicity
  • Relapse
  • Secondary malignancies
  • Infertility

Prognosis

Prognosis is generally excellent in children, with modern treatment achieving very high cure rates. Outcomes in adults are less favorable but have improved substantially with risk-adapted therapy, targeted treatments, and immunotherapies. Prognosis depends on age, initial WBC count, genetic abnormalities, CNS involvement, and minimal residual disease (MRD) response

Key Points / Clinical Pearls

  • Acute Lymphoblastic Leukemia (ALL) is a malignancy of immature lymphoid cells.
  • It is the most common childhood cancer.
  • It may be B-cell or T-cell lineage.
  • Common presentation: pallor + fever + infections + bleeding + bone pain.
  • CBC may show anemia, thrombocytopenia, and abnormal WBC count.
  • Bone marrow examination confirms the diagnosis.
  • Flow cytometry determines lineage.
  • Cytogenetic/molecular testing is essential for risk stratification.
  • CNS-directed therapy is an essential component of treatment.
  • Treatment consists of induction → consolidation/intensification → maintenance.
  • BCR-ABL1-positive ALL requires a tyrosine kinase inhibitor.
  • MRD is an important prognostic and treatment-response marker.
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