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D&T - E1 > Pathoma - White Blood Cell Disorders > Flashcards

Pathoma - White Blood Cell Disorders Flashcards

1
Q

Basic Principles of Leukopenia and Leukocytosis

A
  • Hematopoiesis occurs via a stepwise maturation of CD34+ hematopoietic stem cells
  • Cells mature and are released from the bone marrow into the blood
  • A normal white blood cell (WBC) count is approximately 5-10K/uL
  • LEUKOPENIA = a low WBC count
  • LEUKOCYTOSIS = a high WBC count
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2
Q

Neutropenia

A

Decreased number of circulating neutrophils

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3
Q

Causes of neutropenia

A
  • DRUG TOXICITY (eg chemotherapy with alkylating agents): damage to stem cells results in decreased production of WBCs, especially neutrophils
  • SEVERE INFECTION (eg gram negative sepsis): increased movement of neutrophils into tissues results in decreased circulating neutrophils
  • As a treatment GM-CSF or G-CSF may be used to boost granulocyte production, thereby decreasing risk of infection in neutropenic
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4
Q

Lymphopenia

A

Decreased number of circulating lymphocytes

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5
Q

Causes of lymphopenia

A
  • IMMUNODEFICIENCY (eg DiGeorge syndrome or HIV)
  • HIGH CORTISOL STATE (eg exogenous corticosteroids or Cushing syndrome): induces apoptosis of lymphocytes
  • AUTOIMMUNE DESTRUCTION (eg systemic lupus erythematous)
  • WHOLE BODY RADIATION: lymphocytes are highly sensitive to radiation; lymphopenia is the earliest change to emerge after whole body radiation
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6
Q

Neutrophilic leukocytosis

A

Increased circulating neutrophils

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7
Q

Causes of neutrophilic leukocytosis

A
  • BACTERIAL INFECTION OR TISSUE NECROSIS: induces release of marginated pool and bone marrow neutrophils, including immature forms (LEFT SHIFT); immature cells are characterized by DECREASED Fc receptors (CD16)
  • HIGH CORTISOL STATE: impairs leukocyte adhesion, leading to release of marginated pool of neutrophils
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8
Q

Monocytosis

A

Refers to increased circulating monocytes

Causes:

  • Chronic inflammatory states (eg autoimmune and infectious)
  • Malignancy
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9
Q

Eosinophilia

A

Increased circulating eosinophils. DRIVEN BY INCREASED EOSINOPHIL CHEMOTACTIC FACTOR.

Causes:

  • Allergic reactions (type I hypersensitivity)
  • Parasitic infections
  • Hodgkin lymphoma
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10
Q

Basophilia

A

Increased circulating basophils

Causes:
- Chronic myeloid leukemia

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11
Q

Lymophocytic leukocytosis

A

Increased circulating lymphocytes

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12
Q

Causes of lymphocytic leukocytosis

A
  • VIRAL INFECTIONS: T lymphocytes undergo hyperplasia in response to virally infected cells
  • BORDATELLA PERTUSSIS INFECTION: bacteria produce lymphocytosis-promoting factor, which blocks circulating lymphocytes from leaving the blood to enter the lymph node
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13
Q

Infectious mononucleosis - Causes

A
  • EBV infection that results in a lymphocytic leukocytosis comprised of reactive CD8+ T cells
  • CMV is a less common cause
  • EBV is transmitted by saliva (“kissing disease”); classically affects teenagers
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14
Q

Infectious mononucleosis - EBV infection

A

EBV primarily infects:

  1. OROPHARYNX, resulting in pharyngitis
  2. LIVER, resulting in hepatitis with hepatomegaly and elevated liver enzymes
  3. B CELLS
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15
Q

Infectious mononucleosis - CD8+ T Cell responses leads to

A
  1. Generalized lymphadenophathy (LAD) due to T cell hyperplasia in the lymph node PARACORTEX
  2. Splenomegaly due to T cell hyperplasia in the periarterial lymphatic sheath (PALS)
  3. High WBC count with atypical lymphocytes (reactive CD8+ T cells) in the blood
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16
Q

Infectious mononucleosis - Monospot test

A
  • Used for screening
  • Detects IgM antibodies that cross-react with horse or sheep RBC (HETEROPHILE ANTIBODIES)
  • Usually positive within 1 week after infection
  • A negative monospot test suggests CMV as a possible cause of infectious mononucleosis
  • Definitive diagnosis is made by serologic testing for the EBV viral capsid antigen
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17
Q

Infectious mononucleosis - Complications

A
  • Increased risk for splenic rupture (patients are generally advised to avoid contact sports for one month)
  • Rash if exposed to penicillins/ampicillin
  • Dormancy of virus in B cells leads to increased risk for both recurrence and B cell lymphoma, especially if immunodeficiency (eg HIV) develops
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18
Q

Acute Leukemia - Basic principles

A
  • Neoplastic proliferation of blasts; defined as the accumulation of >20% blasts in the bone marrow
  • Increased blasts “crowd-out” normal hematopoiesis, resulting in an “ACUTE” presentation with ANEMIA (fatigue), THROMBOCYTOPENIA (bleeding), or NEUTROPENIA (infection)
  • Blasts usually enter the blood stream, resulting in a HIGH WBC count (blasts are large, immature cells, often with PUNCHED OUT NUCLEOLI)
  • Acute leukemia is subdivided into ACUTE LYMPHOBLASTIC LEUKEMIA (ALL) or ACUTE MYELOGENOUS LEUKEMIA (AML) based on the phenotype of the blasts
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19
Q

Acute lymphoblastic leukemia

A

Neoplastic accumulation of lymphoblasts (>20%) in the bone marrow

  • Lymphoblasts are characterized by positive nuclear staining for TdT, a DNA polymerase
  • TdT is ABSENT in myeloid blasts and mature lymphocytes
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20
Q

Acute lymphoblastic leukemia - Occurrence

A
  • Most commonly arises in children

- Associated with Down syndrome (usually arises AFTER the age of 5)

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21
Q

Acute lymphoblastic leukemia - Subclassifications

A

B-ALL and T-ALL → based on SURFACE MARKERS

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22
Q

Acute lymphoblastic leukemia - B-ALL

A
  • Most common type of ALL
  • Usually characterized by lymphoblasts (TdT+) that express CD10, CD19 and CD20
  • Excellent response to chemotherapy
  • Requires prophylaxis to SCROTUM and CSF
  • Prognosis is based on cytogenetic abnormalities
  • t(12;21) has a GOOD prognosis; more commonly seen in CHILDREN
  • t(9;22) has a POOR prognosis; more commonly seen in adults (Philadelphia+ ALL)
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23
Q

Acute lymphoblastic leukemia - T-ALL

A
  • Characterized by lymphoblasts (TdT+) that express markers ranging from CD2 - CD8
  • The blasts do NOT express CD10
  • Usually presents in TEENAGERS as a mediastinal (THYMIC) mass
  • Called acute lymphoblastic LYMPHOMA because the malignant cells form a mass
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24
Q

Acute myeloid leukemia

A

Neoplastic accumulation of immature myeloid cells (>20%) in the bone marrow

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25
Q

Acute myeloid leukemia - Characterization

A

Usually characterized by positive staining for MYEOPEROXIDASE (MPO)
- Crystal aggregates of MPO may be seen as AUER RODS

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26
Q

Acute myeloid leukemia - Occurrence

A

Most commonly arises in older adults (average age 50-60 years)

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27
Q

Acute myeloid leukemia - Subtypes

A
  • Acute promyelocytic leukemia (APL)
  • Acute monocytic leukemia
  • Acute megakaryoblastic leukemia
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28
Q

Acute myeloid leukemia - Acute promyelocytic leukemia

A
  • Characterized by t(15;17) which involves translocation of the retinoic acid receptor (RAR) on chromosome 17 to chromosome 15
  • RAR disruption blocks maturation and promyelocytes (blasts) accumulate
  • Abnormal promyelocytes contain numerous primary granules that increase risk for DIC
  • Treatment is with all-trans-retinoic acid (ATRA; a vitamin A derivative), which binds the altered receptor and causes the blasts to mature (and eventually die)
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29
Q

Acute myeloid leukemia - Acute monocytic leukemia

A
  • Proliferation of monoblasts
  • Usually lack MPO
  • Blasts characteristically infiltrate GUMS
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30
Q

Acute myeloid leukemia - Acute megakaryoblastic leukemia

A
  • Proliferation of megakaryoblasts
  • Usually lack MPO
  • Associated with DOWN SYNDROME (usually arises BEFORE the age of 5)
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31
Q

Acute myeloid leukemia arising from pre-existing dysplasia

A
  • AML may arise from pre-existing dysplasia (MYELODYSPLASTIC SYNDROMES) especially with prior exposure to alkylating agents or radiotherapy
  • Myelodysplastic syndromes usually present with CYTOPENIAS, HYPERCELLULAR BONE MARROW, ABNORMAL MATURATION OF CELLS, and INCREASED BLASTS (>20%)
  • Most patients die from INFECTION or BLEEDING, though some progress to acute leukemia
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32
Q

Chronic Leukemia - Basic Principles

A
  • Neoplastic proliferation of mature circulating lymphocytes
  • Characterized by a HIGH WBC count
  • Usually insidious in onset and seen in older adults

Includes:

  • Chronic lymphocytic leukemia (CLL)
  • Hairy cell leukemia
  • Adult T cell leukemia/lymphoma (ATLL)
  • Mycosis fungoides
33
Q

Chronic lymphocytic leukemia

A
  • Neoplastic proliferation of naïve B cells that co-express CD5 and CD20 → MOST COMMON LEUKEMIA
  • Increased lymphocytes and SMUDGE CELLS are seen on blood smear
  • Involvement of lymph nodes leads to generalized lymphadenopathy and is called SMALL LYMPHOCYTIC LYMPHOMA

Complications:

  • HYPOGAMMAGLOBULINEMIA - infection is the most common cause of death in CLL
  • Autoimmune hemolytic anemia
  • Transformation of diffuse large B cell lymphoma (RICHTER TRANSFORMATION) - marked clinically by an enlarging lymph node or spleen
34
Q

Hairy cell leukemia

A
  • Neoplastic proliferation of mature B cells characterized by hairy cytoplasmic processes
  • Cells are positive for TARTRATE-RESISTANT ACID PHOSPHATASE (TRAP)
  • Clinical features include SPLENOMEGALY (due to accumulation of hairy cells in red pulp) and DRY TAP on bone marrow aspiration (due to marrow fibrosis)
  • LYMPHADENOPATHY IS USUALLY ABSENT
  • Excellent response to 2-CDA (cladribine) an adenosine deaminase inhibitor (adenosine accumulates to toxic levels in neoplastic B cells)
35
Q

Adult T cell leukemia/lymphoma

A
  • Neoplastic proliferation of mature CD4+ T cells
  • Associated with HTLV-1 (most commonly seen in Japan and Carribbean)
  • Clinical features include RASH (skin infiltration), generalized LYMPHADENOPATHY with HEPATOSPLENOMEGALY, and LYTIC (punched out) bone lesions with hypercalcemia
36
Q

Mycosis fungoides

A
  • Neoplastic proliferation of mature CD4+ T cells that infiltrate the skin, producing localized skin rash, plaques and nodules
  • Aggregates of neoplastic cells in the epidermis are called PAUTRIER MICROABSCESSES
  • Cells can spread to involve the blood, producing SEZARY SYNDROME (characteristic lymphocytes with cerebriform nuclei - Sezary cells - are seen on blood smear)
37
Q

Myeloproliferative Disorders - Basic Principles

A
  • Neoplastic proliferation of mature cells of myeloid lineage
  • Disease of LATE adulthood (avg age is 50-60 years old)
  • Results in HIGH WBC count with hypercellular bone marrow (cells of all myeloid lineages are increased, CLASSIFIED BASED ON THE DOMINANT MYELOID CELL PRODUCED)
  • Complications include: increased risk for HYPERURICEMIA and GOUT due to high turnover of cells; progression to BONE MARROW FIBROSIS or transformation to ACUTE LEUKEMIA

Includes:

  • Chronic myeloid leukemia (CML)
  • Polycythemia vera (PV)
  • Essential thrombocythemia (ET)
  • Myelofibrosis
38
Q

Chronic myeloid leukemia

A
  • Neoplastic proliferation of mature myeloid cells, especially granulocytes and their precursors
  • BASOPHILS are characteristically increased
39
Q

Chronic myeloid leukemia - Cause

A
  • Driven by t(9;22) (Philadelphia chromosome) which generates a BCR-ABL fusion protein with INCREASED TYROSINE KINASE activity
  • First line treatment is IMANTIB, which blocks tyrosine kinase acitivity
40
Q

Chronic myeloid leukemia - Symptoms

A
  • SPLENOMEGALY is common
  • Enlargening spleen suggests progression to accelerated phase of disease → transformation to acute leukemia usually follows shortly thereafter
  • Can transform to AML (2/3 of cases) or ALL (1/3 of cases) since MUTATION IS IN PLURIPOTENT STEM CELL
41
Q

Chronic myeloid leukemia vs Leukomoid reaction (reactive neutrophilic leukocytosis)

A
  • Negative leukocyte alkaline phosphatase (LAP) stain (granulocytes in a leukomoid reaction are LAP positive)
  • Increased basophils (absent with leukemoid reaction)
  • t(9;22) (absent in leukomoid reaction)
42
Q

Polycythemia vera

A
  • Neoplastic proliferation of mature myeloid cells, ESPECIALLY RBCs
  • Granulocytes and platelets are also increased
43
Q

Polycythemia vera - Cause

A

Associated with a JAK2 kinase mutation

44
Q

Polycythemia vera - Symptoms

A
  • Mostly due to the HYPERVISCOSITY of blood
  • Blurry vision and headache
  • Increased venous thrombosis (eg hepatic vein, portal vein, and dural sinus)
  • Flushed face due to congestion (plethora)
  • Itching, especially after bathing (due to histamine release from increased mast cells)
45
Q

Polycythemia vera - Treatment

A
  • First line: phlebotomy
  • Second line: hydroxyurea
  • Without treatment, death usually occurs within one year
46
Q

Polycythemia vera vs Reactive polycythemia

A
  • In PV, erythropoietic (EPO) levels are decreased and saturation of O2 is normal
  • In reactive polycythemia due to high altitude or lung disease, saturation of O2 is low and EPO is increased
  • In reactive polycythemia due to ectopic EPO production from renal cell carcinoma, EPO is high and saturation of O2 is normal
47
Q

Essential thrombocytopenia

A
  • Neoplastic proliferation of mature myeloid cells, especially PLATELETS
  • RBCs and granulocytes are also increased
48
Q

Essential thrombocytopenia - Cause

A

Associated with JAK2 kinase mutation

49
Q

Essential thrombocytopenia - Symptoms

A
  • Associated with increased risk of bleeding and/or thrombosis
  • Rarely progresses to marrow fibrosis or acute leukemia
  • No significant risk for hyperuricemia or gout
50
Q

Myelofibrosis

A

Neoplastic proliferation of mature myeloid cell, especially megakaryocytes

51
Q

Myelofibrosis - Cause

A
  • Associated with JAK2 kinase mutation in 50% of cases

- Megakaryocytes produce excess PLATELET DERIVED GROWTH FACTOR (PDGF) causing bone marrow fibrosis

52
Q

Myelofibrosis - Symptoms

A
  • SPLENOMEGALY due to extramedullary hematopoiesis
  • LEUKOERYTHROBLASTIC SMEAR (tear drop RBCs, nucleated RBCs and immature granulocytes)
  • Increased risk for infection, thrombosis, and bleeding
53
Q

Lymphadenopathy - Basic Principles

A
  • Refers to enlarged lymph nodes
  • PAINFUL LAD is usually seen in lymph nodes that are draining a region of ACUTE infection (ACUTE LYMPHADENITIS)
  • PAINLESS LAD is usually seen with CHRONIC inflammation (CHRONIC LYMPHADENITIS), METASTATIC CARCINOMA or LYMPHOMA
54
Q

Lymphadenopathy - Inflammation

A
  • FOLLICULAR HYPERPLASIA (B cell region) is seen with rheumatoid arthritis and early stages of HIV infection, for example
  • PARACORTEX HYPERPLASIA (T cell region) is seen with viral infections (eg infectious mononucleosis)
  • HYPERPLASIA OF SINUS HISTIOCYTES is seen in lymph nodes that are draining tissue with cancer
55
Q

Lymphoma - Basic Principles

A
  • Neoplastic proliferation of lymphoid cells that forms a mass
  • May arise in a lymph node or in extranodal tissue
  • Divided into non-Hodgkin lymphoma (NHL, 60%) and Hodgkin lymphoma (HL, 40%)

NHL is further classified based on cell type, cell size, pattern of cell growth, expression of surface markers, and cytogenetic translocations:

  1. Small B cells: follicular lymphoma, mantle cell lymphoma (eg CLL cells that involve tissue)
  2. Intermediate sized B cells: Burkitt lymphoma
  3. Large B cells: diffuse large B cell lymphoma
56
Q

Follicular Lymphoma

A
  • Neoplastic proliferation of small B cells (CD20+) that form follicle-like nodules
  • Presents in late adulthood with painless lymphadenopathy
57
Q

Follicular Lymphoma - Causes

A
  • Driven by t(14;18)
  • BCL2 on chromosome 18 translocates to the Ig heavy chain locus on chromosome 14
  • Results in overexpression of Bcl2, which inhibits apoptosis
58
Q

Follicular Lymphoma - Treatment

A

Treatment is reserved for patients who are symptomatic and involves low dose chemotherapy or RITUXIMAB (anti-CD20 antibody)

59
Q

Follicular lymphoma - Complications

A

Progression to diffuse large B cell lymphoma is an important complication; presents as an enlarging lymph node

60
Q

Follicular lymphoma vs Follicular hyperplasia

A

Follicular lymphoma is distinguished from reactive follicular hyperplasia by

  • Disruption of normal lymph node architecture (maintained in follicular hyperplasia)
  • Lack of tangible body macrophages in germinal centers (tangible body macrophages are present in follicular hyperplasia)
  • Bcl2 expression in follicles (not expressed in follicular hyperplasia)
  • Monoclonality (follicular hyperplasia is polyclonal)
61
Q

Mantle cell lymphoma

A
  • Neoplastic proliferation of small B cells (CD20+) that expands the marginal zone
  • Associated with chronic inflammatory states such as Hashimoto’s thyroiditis, Sjogren syndrome and H pylori gastritis (the marginal zone is formed by post-germinal center B cells)
  • MALToma is marginal zone lymphoma in mucosal sites (Gastric MALToma may regress with treatment of H pylori)
62
Q

Burkitt lymphoma

A
  • Neoplastic proliferation of intermediate sized B cells (CD20+)
  • Associated with EBV
  • Classically presents as an extranodal mass in a child or young adult
  • African form usually involves the JAW
  • Sporadic form usually involves the ABDOMEN
63
Q

Burkitt lymphoma - Cause

A
  • Driven by translocations of c-myc (chromosome 8)
  • t(8;14) is most common, resulting in translocation of c-myc to the Ig heavy chain locus on chromosome 14
  • Overexpression of c-myc oncogene promotes cell growth
64
Q

Burkitt lymphoma - Characterization

A

Characterized by high mitotic index and ‘starry-sky’ appearance on microscopy

65
Q

Diffuse large B cell lymphoma

A
  • Neoplastic proliferation of large B cells (CD20+) that grow diffusely in sheets
  • MOST COMMON FORM OF NHL
  • Clinically aggressive (high grade)
  • Arises sporadically or from transformation of a low grade lymphoma
  • Present in late adulthood as an enlarging lymph node or an extranodal mass
66
Q

Hodgkin Lymphoma - Basic principles

A
  • Neoplastic proliferation of Reed-Sternberg (RS) cells which are large B cells with multilobed nuclei and prominent nucleoli (owl-eyed nuclei)
  • Classically positive for CD15 and CD30
67
Q

Hodgkin Lymphoma - Reed-Sternberg cells

A

RS cells secrete cytokines:

  • Occasionally result in B symptoms (fever, chills, weight loss and night sweats)
  • Attract reactive lymphocytes, plasma cells, macrophages, and eosinophils
  • May lead to fibrosis
68
Q

Hodgkin lymphoma - Subtypes

A

Reactive inflammatory cells make up a bulk of the tumor and form the basis for classification of HL. Subtypes include:

  • Nodcular sclerosis
  • Lymphocyte rich
  • Mixed cellularity
  • Lymphocyte depleted
69
Q

Hodgkin lymphoma - Nodular sclerosis

A
  • MOST COMMON SUBTYPE OF HL (70% of all cases)
  • Classic presentation is an enlarging cervical or mediastinal lymph node in a young adult, usually female
  • Lymph node is divided by bands of sclerosis
  • RS cells are present in lake-like spaces (lacunar cells)
70
Q

Hodgkin lymphoma - Other subtypes

A
  • Lymphocyte rich has the best prognosis of all types
  • Mixed cellularity is often associated with abundance eosinophils (RS cells produce IL-5)
  • Lymphocyte-depleted is the most aggressive of all types; usually seen in the elderly and HIV positive individuals
71
Q

Mutltiple myeloma

A

Malignant proliferation of plasma cells in the bone marrow

  • Most common primary malignancy of bone (metastatic cancer, however, is the most common malignant lesion of the bone overall)
  • High serum IL-6 may be present; stimulates plasma cell growth and immunoglobulin production
72
Q

Multiple myeloma - Symptoms

A
  • BONE PAIN with HYPERCALCEMIA: neoplastic plasma cells activate the RANK receptor on osteoclasts, leading to bone destruction
  • Lytic, punched out skeletal lesions are seen on x-ray, especially in the vertebrae and skull
  • Increased risk for fracture
  • ELEVATED SERUM PROTEIN: neoplastic plasma cells produce immunoglobulin; M spike is present on serum protein electrophoresis (SPEP), most commonly due to monoclonal IgG or IgA
  • INCREASED RISK FOR INFECTION: monoclonal antibody lacks antigenic diversity; infection is the most common cause of death in multiple myeloma
  • ROULEAUX FORMATION OF RBC ON BLOOD SMEAR: increased serum protein decreases charge between RBCs
  • PRIMARY AL AMYLOIDOSIS: free light chains circulate in serum and deposit in tissues
  • PROTEINURIA: free light chain is excreted in the urine as Bence Jones protein; deposition in kidney tubules leads to risk for renal failure (myeloma kidney)
73
Q

Monoclonal gammopathy of undetermined significance (MGUS)

A
  • Increased serum protein with M spike on SPEP
  • Other features of multiple myeloma are absent (eg no lytic bone lesions, hypercalcemia, AL amyloid, or Bence Jones proteinuria)
  • Commonly seen in elderly (seen in 5% of 70 year old individuals)
  • 1% of patients with MGUS develop multiple myeloma each year
74
Q

Waldenstrom Macroglobulinemia

A
  • B cell lymphoma with monoclonal IgM production
  • Acute complications are treated with plasmapharesis, which removes IgM from the serum

Clinical features include:

  • Generalized lymphadenopathy; lytic bone lesions are absent
  • Increased serum protein with M spike (compromised IgM)
  • Visual and neurologic deficits (eg retinal hemorrhage or stroke) - IgM (large pentamer) causes serum hyperviscosity
  • Bleeding: viscous serum results in defective platelet aggregation
75
Q

Langerhans cell histiocytes - Basic principles

A

Langerhans cells are specialized dendritic cells found predominantly in the skin

  • Derived from bone marrow monocytes
  • Present antigen to naïve T cell

Langerhans cell histiocytosis is a neoplastic proliferation of Langerhans cells

  • Characteristic Birbeck (tennis racket) granules are seen on electron microscopy
  • Cells are CD1a+ and S100+ by immunohistochemistry
76
Q

Letterer-SIWE disease

A
  • Malignant proliferation of Langerhans cells

- Classic presentation is skin rash and cystic skeletal defects in an infant (

77
Q

Eosinophilic granuloma

A
  • Benign proliferation of Langerhans cells in bone
  • Classic presentation is pathologic fracture in an adolescent; skin is not involved
  • Biopsy shows Langerhans cells with mixed inflammatory cells, including numerous eosinophils
78
Q

Hand-Schuller-Christian disease

A
  • Malignant proliferation of Langerhans cells
  • Classic presentation is scalp rash, lytic skull defects, diabetes insipidus, and exophthalmos in a child

EXOPHTHALMOS = abnormal protrusion of the eyeball(s)

D&T - E1 (11 decks)

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