Chronic lymphocytic leukemia (CLL) is the most common leukemia in Western countries, characterized by clonal expansion of mature-appearing CD5+ B lymphocytes in blood, bone marrow, and lymphoid tissues. The clinical course is highly variable, ranging from indolent disease requiring no treatment to aggressive forms. Prognosis is stratified by IGHV mutation status, cytogenetics (del(17p), del(11q), del(13q)), and TP53 mutations. Treatment has been revolutionized by BTK inhibitors (ibrutinib, acalabrutinib) and BCL2 inhibitors (venetoclax), enabling chemotherapy-free regimens with deep remissions.
name: Chronic Lymphocytic Leukemia
creation_date: '2026-01-26T02:55:13Z'
updated_date: '2026-03-13T12:00:00Z'
description: >-
Chronic lymphocytic leukemia (CLL) is the most common leukemia in Western countries,
characterized by clonal expansion of mature-appearing CD5+ B lymphocytes in blood,
bone marrow, and lymphoid tissues. The clinical course is highly variable, ranging
from indolent disease requiring no treatment to aggressive forms. Prognosis is
stratified by IGHV mutation status, cytogenetics (del(17p), del(11q), del(13q)),
and TP53 mutations. Treatment has been revolutionized by BTK inhibitors (ibrutinib,
acalabrutinib) and BCL2 inhibitors (venetoclax), enabling chemotherapy-free regimens
with deep remissions.
categories:
- Hematologic Malignancy
- B-cell Neoplasm
- Chronic Leukemia
- Lymphoproliferative Disorder
parents:
- B-cell neoplasm
epidemiology:
- name: Most common adult leukemia
description: Chronic lymphocytic leukemia is the most common type of leukemia in adults.
evidence:
- reference: PMID:41572562
reference_title: "\"Leukemic pernio\": perniosis-like presentations of chronic lymphocytic leukemia."
supports: SUPPORT
snippet: "Chronic lymphocytic leukemia (CLL) is the most common type of leukemia in adults."
explanation: This abstract explicitly states that CLL is the most common adult leukemia.
has_subtypes:
- name: IGHV Mutated CLL
description: >-
CLL with somatic hypermutation of immunoglobulin heavy chain variable region
genes (at least 2% deviation from germline). Associated with favorable prognosis,
lower risk of progression, and better responses to chemoimmunotherapy. Represents
post-germinal center B-cell origin.
- name: IGHV Unmutated CLL
description: >-
CLL without significant IGHV somatic hypermutation (less than 2% deviation from
germline). Associated with more aggressive course, higher risk of progression,
and inferior outcomes with chemoimmunotherapy. May benefit particularly from
novel targeted agents.
pathophysiology:
- name: B-cell Receptor Signaling Dysregulation
description: >-
CLL cells exhibit constitutive B-cell receptor (BCR) signaling, either through
autonomous signaling or antigen-driven activation. This chronic BCR stimulation
activates downstream kinases including BTK, PI3K, and SYK, driving proliferation
and survival. BCR signaling intensity correlates with clinical aggressiveness.
cell_types:
- preferred_term: mature B cell
term:
id: CL:0000785
label: mature B cell
biological_processes:
- preferred_term: B cell activation
modifier: INCREASED
term:
id: GO:0042113
label: B cell activation
downstream:
- target: BTK Pathway Activation
description: BCR engagement activates BTK-mediated survival signaling
- target: Microenvironmental Survival Signals
description: BCR signaling facilitates interaction with supportive niches
- name: BTK Pathway Activation
description: >-
Bruton tyrosine kinase (BTK) is essential for BCR signaling and CLL cell survival.
BTK activation promotes NF-kB signaling, cell adhesion, and tissue homing.
BTK inhibitors disrupt these signals, mobilizing CLL cells from protective
tissue microenvironments and inducing apoptosis.
biological_processes:
- preferred_term: signal transduction
modifier: INCREASED
term:
id: GO:0007165
label: signal transduction
downstream:
- target: NF-kB Activation and Survival
description: BTK activates NF-kB-mediated anti-apoptotic gene expression
- name: Microenvironmental Survival Signals
description: >-
CLL cells depend on interactions with the tissue microenvironment including
nurse-like cells, T cells, and stromal cells in lymph nodes and bone marrow.
These interactions provide survival signals through chemokines, cytokines,
and direct cell contact. Disrupting these interactions is therapeutically
important.
locations:
- preferred_term: lymph node
term:
id: UBERON:0000029
label: lymph node
- preferred_term: bone marrow
term:
id: UBERON:0002371
label: bone marrow
cell_types:
- preferred_term: B cell
term:
id: CL:0000236
label: B cell
downstream:
- target: CLL Cell Accumulation
description: Microenvironmental support enables CLL expansion
- name: NF-kB Activation and Survival
description: >-
NF-kB transcription factors are constitutively activated in CLL and promote
expression of anti-apoptotic genes including BCL2, MCL1, and XIAP. This
contributes to the apoptosis resistance characteristic of CLL cells.
biological_processes:
- preferred_term: apoptotic process
modifier: DECREASED
term:
id: GO:0006915
label: apoptotic process
downstream:
- target: CLL Cell Accumulation
description: Anti-apoptotic signaling enables CLL cell accumulation
- name: CLL Cell Accumulation
description: >-
The combination of defective apoptosis, microenvironmental support, and
low-level proliferation leads to progressive accumulation of clonal B cells.
CLL is primarily a disease of accumulation rather than rapid proliferation.
cell_types:
- preferred_term: B cell
term:
id: CL:0000236
label: B cell
histopathology:
- name: Small B-Cell Clonal Expansion
finding_term:
preferred_term: Small Lymphocytic Lymphoma
term:
id: NCIT:C7540
label: Small Lymphocytic Lymphoma
frequency: VERY_FREQUENT
description: Chronic lymphocytic leukemia is characterized by clonal expansion of CLL B cells.
evidence:
- reference: PMID:29670635
reference_title: "Chronic Lymphocytic Leukemia B-Cell Normal Cellular Counterpart: Clues From a Functional Perspective."
supports: SUPPORT
snippet: "Chronic lymphocytic leukemia (CLL) is characterized by the clonal expansion of"
explanation: Abstract describes CLL as characterized by clonal expansion of CLL B cells.
phenotypes:
- category: Hematologic
name: Lymphoproliferative Disorder
frequency: VERY_FREQUENT
diagnostic: true
description: >-
Persistent elevation of blood lymphocyte count (at least 5000/uL clonal
B lymphocytes) is required for CLL diagnosis. Many patients are diagnosed
incidentally from routine blood tests.
phenotype_term:
preferred_term: Lymphoproliferative disorder
term:
id: HP:0005523
label: Lymphoproliferative disorder
- category: Lymphatic
name: Lymphadenopathy
frequency: VERY_FREQUENT
description: >-
Enlarged lymph nodes are common, may be generalized, and can become
massive. Lymph node involvement is incorporated in staging systems.
phenotype_term:
preferred_term: Lymphadenopathy
term:
id: HP:0002716
label: Lymphadenopathy
evidence:
- reference: PMID:1139039
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "stage 1, lymphocytosis with enlarged nodes"
explanation: The Rai staging system defines Stage I CLL by the presence of lymphadenopathy (enlarged nodes), confirming its clinical significance.
- category: Abdominal
name: Splenomegaly
frequency: FREQUENT
description: >-
Spleen enlargement from CLL infiltration. Massive splenomegaly may
cause cytopenias from sequestration.
phenotype_term:
preferred_term: Splenomegaly
term:
id: HP:0001744
label: Splenomegaly
evidence:
- reference: PMID:1139039
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "stage II, lymphocytosis with enlarged spleen or liver or both"
explanation: The Rai staging system defines Stage II CLL by the presence of splenomegaly or hepatomegaly, confirming splenomegaly as a key clinical feature.
- category: Hematologic
name: Anemia
frequency: FREQUENT
description: >-
Anemia may result from bone marrow infiltration, autoimmune hemolytic
anemia (AIHA), or hypersplenism.
phenotype_term:
preferred_term: Anemia
term:
id: HP:0001903
label: Anemia
- category: Hematologic
name: Thrombocytopenia
frequency: FREQUENT
description: >-
Low platelet count from marrow infiltration, immune thrombocytopenia
(ITP), or hypersplenism.
phenotype_term:
preferred_term: Thrombocytopenia
term:
id: HP:0001873
label: Thrombocytopenia
- category: Infectious
name: Recurrent Infections
frequency: FREQUENT
description: >-
Increased susceptibility to bacterial and viral infections due to
hypogammaglobulinemia and immune dysfunction. Herpes zoster and
respiratory infections are common.
phenotype_term:
preferred_term: Recurrent infections
term:
id: HP:0002719
label: Recurrent infections
evidence:
- reference: PMID:18755702
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Patients with chronic lymphocytic leukaemia (CLL) have progressive immunodeficiency and infection is the commonest cause of death."
explanation: This authoritative review establishes that infection due to immunodeficiency is the leading cause of death in CLL patients.
- category: Constitutional
name: Night Sweats
frequency: OCCASIONAL
description: >-
B symptoms including night sweats indicate more active disease and
may warrant treatment initiation.
phenotype_term:
preferred_term: Night sweats
term:
id: HP:0030166
label: Night sweats
- category: Constitutional
name: Weight Loss
frequency: OCCASIONAL
description: >-
Unintentional weight loss is a B symptom indicating active disease.
phenotype_term:
preferred_term: Weight loss
term:
id: HP:0001824
label: Weight loss
biochemical:
- name: Flow Cytometry Immunophenotyping
notes: >-
CLL cells are CD5+, CD19+, CD23+, CD20 dim, surface Ig dim. The
characteristic immunophenotype distinguishes CLL from other B-cell
lymphomas and mantle cell lymphoma (CD5+ but CD23-).
- name: IGHV Mutation Analysis
notes: >-
Sequencing of immunoglobulin heavy chain variable region determines
mutational status. Mutated IGHV (at least 2% difference from germline)
indicates favorable prognosis.
genetic:
- name: TP53 Mutation/del(17p)
association: High-Risk Prognostic Marker
notes: >-
TP53 alterations (mutation or del(17p)) occur in 5-10% at diagnosis,
higher in relapsed disease. Confer resistance to chemoimmunotherapy
and poor prognosis. BTK and BCL2 inhibitors remain effective.
- name: del(11q)/ATM
association: Intermediate-Risk Marker
notes: >-
Deletion of 11q23 affects the ATM gene, impairing DNA damage responses.
Associated with bulky lymphadenopathy and intermediate prognosis.
May benefit from targeted therapies.
- name: del(13q)
association: Favorable Prognostic Marker
notes: >-
Isolated del(13q14) is the most common cytogenetic abnormality in CLL
and is associated with favorable prognosis when present alone. This
region contains microRNA genes miR-15a and miR-16-1.
- name: IGHV
association: Prognostic Marker
notes: >-
IGHV mutation status is one of the strongest prognostic markers in CLL.
Mutated IGHV indicates post-germinal center origin with better prognosis.
Unmutated IGHV indicates more aggressive disease course.
treatments:
- name: Ibrutinib
description: >-
First-in-class irreversible BTK inhibitor that disrupts BCR signaling,
mobilizes CLL cells from tissue niches, and induces apoptosis.
Effective in all risk groups including TP53-mutated CLL. Continuous
therapy until progression.
treatment_term:
preferred_term: pharmacotherapy
term:
id: MAXO:0000058
label: pharmacotherapy
therapeutic_agent:
- preferred_term: ibrutinib
term:
id: CHEBI:76612
label: ibrutinib
evidence:
- reference: PMID:26639149
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "ibrutinib resulted in significantly longer progression-free survival than did chlorambucil (median, not reached vs. 18.9 months), with a risk of progression or death that was 84% lower with ibrutinib than that with chlorambucil"
explanation: The landmark RESONATE-2 trial demonstrated ibrutinib's superiority in treatment-naive elderly CLL patients with 84% reduction in risk of progression or death.
- name: Acalabrutinib
description: >-
Second-generation selective BTK inhibitor with improved kinase selectivity
and potentially fewer off-target effects than ibrutinib. Effective as
monotherapy or combined with obinutuzumab.
treatment_term:
preferred_term: pharmacotherapy
term:
id: MAXO:0000058
label: pharmacotherapy
therapeutic_agent:
- preferred_term: acalabrutinib
term:
id: CHEBI:167707
label: acalabrutinib
- name: Venetoclax plus Obinutuzumab
description: >-
BCL2 inhibitor venetoclax combined with anti-CD20 antibody obinutuzumab
achieves high rates of undetectable MRD and enables time-limited
therapy (12 months). Particularly effective in treatment-naive CLL.
treatment_term:
preferred_term: pharmacotherapy
term:
id: MAXO:0000058
label: pharmacotherapy
therapeutic_agent:
- preferred_term: venetoclax
term:
id: CHEBI:133021
label: venetoclax
evidence:
- reference: PMID:30523712
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "The MURANO study demonstrated significant progression-free survival (PFS) benefit for fixed-duration venetoclax-rituximab compared with bendamustine-rituximab in relapsed/refractory chronic lymphocytic leukemia."
explanation: The MURANO Phase III study demonstrated venetoclax-rituximab's superiority in relapsed/refractory CLL with significantly improved progression-free survival.
- name: Chemoimmunotherapy (FCR)
description: >-
Fludarabine, cyclophosphamide, and rituximab combination was standard
for fit patients with mutated IGHV without del(17p)/TP53 mutation.
Can achieve long remissions in this favorable subgroup but largely
replaced by targeted agents.
treatment_term:
preferred_term: chemotherapy
term:
id: MAXO:0000647
label: chemotherapy
therapeutic_agent:
- preferred_term: cyclophosphamide
term:
id: CHEBI:4027
label: cyclophosphamide
- name: Watch and Wait
description: >-
Asymptomatic early-stage CLL does not require immediate treatment.
Active surveillance with monitoring for disease progression or
treatment indications (cytopenias, symptomatic disease, rapid
progression) is appropriate for many patients.
treatment_term:
preferred_term: surveillance for malignancies
term:
id: MAXO:0001492
label: surveillance for malignancies
disease_term:
preferred_term: chronic lymphocytic leukemia
term:
id: MONDO:0004948
label: B-cell chronic lymphocytic leukemia
classifications:
icdo_morphology:
classification_value: Leukemia
harrisons_chapter:
- classification_value: cancer
- classification_value: hematologic malignancy