WBC disorders Flashcards
wbc disorders
Deficiencies (leukopenias) Proliferations -Reactive -Neoplastic *9% of cancer deaths in adults *40% of cancer deaths in children <15 yrs
Leukopenia
Most commonly decrease in granulocytes Lymphopenias are less common -Congenital immunodeficiency states -Acquired *Advanced HIV infection *Corticosteroid treatment
Neutropenia / Agranulocytosis
Decreased numbers of neutrophils
Typically < 1000 cells/µl
Extremely susceptible to bacterial and fungal infections
Neutropenia / Agranulocytosis causes
Inadequate or ineffective granulopoiesis
-Aplastic anemia, leukemia, chemotherapy, other drugs
Accelerated removal or destruction of neutrophils
-Immune-mediated injury (some drug induced)
-Increased peripheral utilization (overwhelming infection)
-Splenic sequestration (enlarged spleen / hypersplenism)
Neutropenia / Agranulocytosis morphology
Depends on the cause
-Increased or decreased granulocytic precursors in marrow
Neutropenia / Agranulocytosis clinical
Malaise, chills, fever, weakness, fatigability
Ulcerative lesions of the mucosa of the mouth and pharynx
Reactive Leukocytosis
Increased numbers of leukocytes that can be caused by microbial or non-microbial stimuli Relatively non-specific Classified by white cell series affected May mimic leukemia (leukemoid reactions) -Acute viral infections in children -Severe chronic infections
Infectious Mononucleosis
Acute, self-limited disease of adolescents and young adults
-Fever, sore throat, generalized lymphadenitis
-Reactive lymphocytes in peripheral blood
-Antibody and T cell response to EBV
-Resolves in 4-6 weeks
B cells that are latently infected by EBV undergo polyclonal activation and proliferation
-These cells produce the heterophil antibodies detected by the monospot test
Infectious Mononucleosis clinical
Virus-specific cytotoxic T cells appear as reactive lymphocytes in the blood
Enlarged spleen (300-500g) is present in most cases
-Fragile and prone to rupture
Liver function is almost always transiently impaired
-Jaundice is unusual
Infectious Mononucleosis
Atypical presentations can be confused with other diseases
-Lymphoma, rubella, viral hepatitis, FUO
A normal immune system is extremely important in controlling the proliferation EBV-infected B cells
-Bone marrow and organ transplant patients
*Post-transplant lymphoproliferative disorder
-X-linked lymphoproliferative disorder
Reactive Lymphadenitis
Infections and non-microbial inflammatory stimuli can cause lymph node enlargement
Can be acute or chronic
Most are non-specific histologically
Acute Nonspecific Lymphadenitis
Most often confined to a local group of lymph nodes
Can be generalized in systemic bacterial or viral infections
Nodes are enlarged and tender
-Nodes show large germinal centers
-Pyogenic organisms may be associated with neutrophil infiltration
*Infection may involve the overlying skin (draining sinuses)
*Nodes may be fluculant (abscess formation)
Chronic Nonspecific Lymphadenitis
Follicular hyperplasia
Paracortical hyperplasia
Sinus histiocytosis
Follicular hyperplasia
B cell activation
-Rheumatoid arthritis, toxoplasmosis, early HIV
Paracortical hyperplasia
T cell activation
-Viruses, post-vaccination, drugs
Sinus histiocytosis
Distention and prominence of sinusoids, infiltration by macrophages
-Often encountered in nodes draining cancers
Cat Scratch Disease
Self-limited lymphadenitis caused by Bartonella henselae
Primarily a disease of childhood (90% are <18 years old)
Regional lymphadenopathy, most in neck or axilla, two weeks after a feline scratch
Lymphadenopathy regresses over the next 2-4 months, in most patients
Cat Scratch Disease
Rarely patients develop encephalitis, osteomyelitis, or thrombocytopenia
Histologically, lymph node shows sarcoid-like granulomas that may undergo central necrosis with the accumulation of neutrophils
-Organism can be visualized only by special techniques
Frequently confused clinically with lymphoma
Neoplastic Proliferations of White Cells
Lymphoid neoplasms
-Non-Hodgkin lymphomas, Hodgkin disease, lymphocytic leukemias, plasma cell dyscrasias and related disorders
Myeloid neoplasms
-Acute myelogenous leukemias, chronic myeloproliferative disorders, myelodysplastic syndromes
Histiocytic neoplasms
-Langerhans cell histiocytoses
Lymphoid Neoplasms
Leukemias
-Primarily involve the marrow with spillage of cells into the blood
Lymphomas
-Produce masses in the lymph nodes and other tissues
Plasma cell dyscrasias
-Masses within bones
-Systemic symptoms due to production of complete or partial monoclonal immunoglobulin
Lymphoid Neoplasms
Despite their tendencies, all lymphoid neoplasms have the potential to spread to lymph nodes and other tissues, especially liver, spleen, and bone marrow
Lymphomas and plasma cell tumors can spill into the blood
Because of the overlap, lymphoid neoplasms can only be distinguished based on the appearance and molecular characteristics of the tumor cells
Lymphoid Neoplasms
Classified based on a combination of morphologic, phenotypic, genotypic, and clinical features
Lymphomas are divided into two groups
-Non-Hodgkin lymphoma (NHL)
-Hodgkin lymphoma
Lymphoid Neoplasms general principles
B- and T-cell tumors are composed of cells arrested or derived from specific stages of their normal differentiation (lineage-specific and maturity markers)
Most common lymphomas of adults are derived from follicular center or post-follicular center B cells (somatic hypermutation and immunoglobulin class switching)
All lymphoid neoplasms are monoclonal (antigen receptor gene and protein analysis)
Lymphoid neoplasms often disrupt normal immune regulatory mechanisms (immunodeficiency or autoimmunity)
Tumor is widely disseminated at the time of diagnosis (only systemic therapy can be curative)
-Only possible exception is Hodgkin lymphoma
Acute Leukemias
Principle pathogenetic problem in acute leukemia is a block in differentiation
- Leads to the accumulation of immature leukemic blasts in the marrow
- Suppresses normal hematopoiesis
- Bone marrow failure
Acute Leukemias clinical symptoms
Abrupt stormy onset
-Present within 3 months of onset of symptoms
Symptoms related to depression of marrow function
-Fatigue, fever, bleeding
Bone pain and tenderness
-Marrow expansion, subperiosteal infiltration
Generalized lymphadenopathy, splenomegaly, and hepatomegaly
-ALL>AML
CNS manifestations
-Headache, vomiting, nerve palsies from meningeal spread
-Children>Adults, ALL>AML
Acute Leukemias lab findings
Blasts in peripheral blood and bone marrow
WBC count: 100,000 cells/µl
Anemia is almost always present
Platelet count usually < 100,000 platelets/µl
Neutropenia is common
Uncommonly blasts may be absent from the peripheral blood (aleukemic leukemia)
Greatly important to distinguish ALL from AML
Precursor B- and T-Cell Lymphoblastic Leukemia/Lymphoma
Aggressive tumors composed of lymphoblasts
Occur predominantly in children and young adults
B and T cell tumors are morphologically indistinguishable
-B-cell appear in bone marrow and peripheral blood as leukemias
-T-cell commonly present as thymus masses and often progress rapidly to a leukemic phase, others seem to involve only the marrow at presentation
-Both take on the appearance of an acute lymphoblastic leukemia (ALL) at some time during their course
ALLs constitute 80% of childhood leukemias
Peak incidence is age 4, most are pre-B-cell
Pre-T-cell is most common in males 15-20 yrs of age
Precursor B- and T-Cell Lymphoblastic Leukemia/Lymphoma
immunophenotyping
TdT positive (95%) Positive for lineage specific markers (B or T)
Pre-B-cell tumors
karyotyping
Good outcome -Hyperdiploidy (>50 chromosomes/cell) is most common -t(12;21) involving TEL1 and AML1 genes Poor outcome -Translocations involving MLL on 11q23 -Philadelphia chromosome
Pre-T-cell tumors
kayotyping
Completely different group of rearrangements
None predict outcome
55-60% have activating mutations in NOTCH1
Precursor B- and T-Cell Lymphoblastic Leukemia/Lymphoma prognosis
Children 2-10 yrs old have the best prognosis
-Most can be cured, 96% achieve remission
-Age is associated with pre-B-cell tumors and “good” chromosomal aberrations
Worse outcome variables
-Male gender
-10 yrs old
-High leukocyte count at diagnosis
Small Lymphocytic Lymphoma/Chronic Lymphocytic Leukemia
Morphologically, phenotypically, and genotypically identical disorders
Differ only in extent of peripheral blood involvement
-Lymphocytosis >4,000/µl is CLL, if not it’s SLL
-Most patients are CLL
CLL is the most common leukemia of adults in the Western world
Small Lymphocytic Lymphoma/Chronic Lymphocytic Leukemia pathophysiology
Neoplasm of mature B cells
The neoplastic B-cells suppress normal B-cell function, often resulting in hypogammaglobulinemia
15% of patients have autoantibodies to red blood cells
Tumor cells tend to displace normal marrow elements with time
Small Lymphocytic Lymphoma/Chronic Lymphocytic Leukemia morphology
Small, mature-looking lymphocytes Lymph nodes, bone marrow, spleen, and liver are involved in almost all cases Absolute lymphocytosis in PB -Neoplastic lymphocytes are fragile -Produces “smudge cells” on smear
Small Lymphocytic Lymphoma/Chronic Lymphocytic Leukemia Immunophenotype
Pan-B-cell markers CD19, CD20, CD23
CD5
Surface Ig
Small Lymphocytic Lymphoma/Chronic Lymphocytic Leukemia Karyotype
50% abnormal
- Trisomy 12
- Deletion 11 and 12
- Translocations rare
Small Lymphocytic Lymphoma/Chronic Lymphocytic Leukemia Molecular
Somatic hypermutation of Ig segments
If absent, worse prognosis
Small Lymphocytic Lymphoma/Chronic Lymphocytic Leukemia clinical
Often asymtomatic at diagnosis
Symptoms include easy fatigability, weight loss, anorexia
Generalized lymphadenopathy and hepatosplenomegaly in 50-60%
Leukocyte count is highly variable from near normal to >200,000
Hypogammaglobulinemia develops late in about 50% (increased susceptibility to bacterial infection)
Autoimmune hemolytic anemia and thrombocytopenia are seen less commonly
Course is variable: mean survival 4-6 years
Tends to transform to more aggressive tumors like a prolymphocytic leukemia or diffuse large B cell lymphoma: mean survival < 1 year
Follicular Lymphoma morphology
40% of adult NHL in the U.S.
Morphology
Lymph nodes effaced by nodular proliferations
Tumor cells resemble normal follicular center B cells
Follicular Lymphoma Immunophenotype/Molecular
Pan-B-cell markers (CD19, CD20, CD10)
BCL6, transcription factor for follicular center transformation
BCL2, not on normal follicular B cells
Somatic hypermutation of Ig genes
Follicular Lymphoma Karyotype
t(14;18) fuses BCL2 to IgH
Leads to inappropriate expression of BCL2 protein, prevents apoptosis
Follicular Lymphoma clinical
Occurs in older persons, M=F
Painless lymphadenopathy (freq generalized), other visceral site involvement is uncommon
Bone marrow is almost always involved at the time on diagnosis
Median survival 7-9 years, not easily curable
40% progress to diffuse large B cell lymphoma, with or without treatment
-Much less curable than de novo tumor
Mantle Cell Lymphoma morphology
4% of NHL, older males Cells resemble normal mantle zone of lymphoid follicles Diffuse or vaguely nodular pattern Marrow involved in majority 20% have peripheral blood involvement Frequent involvement of the GI tract
Mantle Cell Lymphoma Immunophenotype
Surface IgM and IgD
Pan-B-cell markers CD19 and CD20
CD5 (like CLL/SLL)
Cyclin D1 protein
Mantle Cell Lymphoma Karyotype/Molecular
t(11;14), cyclin D1 gene to IgH locus
Dysregulates the expression of cyclin D1
No somatic hypermutation, naïve B cell origin