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Pathology > Red Cell Disorders > Flashcards

Red Cell Disorders Flashcards

1
Q

Blood cellular elements

A

Peripheral blood film (smear)
Bone marrow aspirate
Bone marrow biopsy (tissue section)

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2
Q

Automated complete blood counts (CBC)

A

Red cell part
White cell part
Platelet part

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3
Q

CBC: red cells

A 
Hemoglobin concentration
-Measured spectrophotometrically (HiCN)
Hematocrit
-Fraction of whole blood that is red cells
RBC concentration (RBC count)
-Measured directly by particle counting
-Impedance and/or electro-optical methods
Red cell indices
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4
Q

Red cell indicies

A

MCV (mean cell volume)
-Average volume per red cell
-Measured by impedance and/or electro-optically
MCH (mean cell hemoglobin)
-Average content (mass) of hemoglobin per red cell
MCHC (mean cell hemoglobin concentration)
-Average concentration of hemoglobin in the red cells
RDW (red cell distribution width)
-Coefficient of variation of red cell volume

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5
Q

CBC: Red cells

A 
Hemoglobin (g/dl):  measured
Hematocrit (%):  calculated (MCV x RBC)
RBC count (x106/µl):  measured
MCV (fl):  measured
MCH (pg):  calculated (Hgb/RBC)
MCHC (g/dl):  calculated (Hgb/Hct)
RDW (%):  measured (SD/MCV)
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6
Q

CBC: White cells

A 
WBC count (x103/µl)
Differential count [5 part] (% of total WBC)
Absolute counts (cells/µl)
Lymphocytes
Monocytes
Neutrophils
Eosinophils
Basophils
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7
Q

CBC: platelets

A

Platelet count (x103/µl)
MPV (mean platelet volume) (fl)
PDW (platelet distribution width) (%)

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8
Q

Reticulocyte Count

A

Manual
-Number of Reticulocytes per 100 red cells
Automated
-% Retics
*Normal: 0.5-1.5%
*% counts must be corrected for degree of anemia
-Absolute count
*Normal: 24,000-84,000/µl
3% or 150,000/µl is a useful guide for a good marrow response to moderate anemia

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9
Q

Red Cells on Blood Films

A

Evaluate the size, color, and shape of the red cells
Assess by
-Direct examination of blood film (smear)
-Red cell indices
Correlates with cause of anemia
Helps in choosing logical next steps
Size: Microcytic, normocytic, or macrocytic
Color: Hypochromic or normochromic
Shape: Normal or a variety of possible abnormal forms

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10
Q

Size & color

A 
Normochromic
normocytic
Polychromasia
Hypochromic, microcytic
Macrocytic
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11
Q

Shape

A 
Spherocytes
Eliptocytes
Target cells
Schistocytes
Poikilocytosis
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12
Q

Hemoglobin

A

Tetramer of globin chains
Each chain has a heme prosthetic group capable of binding oxygen
Heme is a porphyrin ring and a coordinated iron atom

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13
Q

Adult blood contains 3 hemoglobins

A

HbA, α2β2, 97% of total
HbF, α2γ2, 3-5%
HbA2, α2δ2, 1.5-3.5%

Normal and variant hemoglobins can be detected and quantified by electrophoresis, HPLC, or isoelectric focusing

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14
Q

Red cell disorders typically manifest as

A

Anemia
-Decreased number of red cells
Polycythemia
-Increased number of red cells

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15
Q

Anemia

A

Reduction of oxygen carrying capacity of blood
-Reduction of red cell mass
-Labs
Decreased hemoglobin concentration (Hgb)
Decreased hematocrit (Hct)
Decreased red cell concentration (RBC count)

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16
Q

Response to Anemia

A

Decreased tissue oxygen tension →
Increased erythropoietin production →
Hyperplasia of erythroid precursors
-May even lead to extramedullary hematopoiesis
Reticulocytosis is the hallmark of increased marrow output of red cells

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17
Q

Anemia clinical

A

Clinical consequences depend upon severity, speed of onset, and mechanism
Pallor, fatigue, and lassitude are common presenting symptoms
Slow onset gives more time to adapt
Premature destruction
-Hyperbilirubinemia, jaundice, pigment gallstones
Ineffective erythropoiesis
-Increased iron absorption, iron overload
Severe congenital anemias
-Growth retardation, skeletal abnormalities, cachexia

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18
Q

Anemia of Blood Loss

A

Acute blood loss

chronic blood loss

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19
Q

Acute blood loss

A

Hypovolemia is the most immediate threat
-Cardiovascular collapse, shock, and death
Fluid volume is fully restored in 2-3 days
-Hemodilution reveals the extent of the anemia
-Normochromic, normocytic anemia
Red cell production increases in several days
-↑ Epo → Erythroid precursors → Red cells

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20
Q

Chronic blood loss

A

Anemia develops when
Rate of blood loss exceeds production capacity
Run out of raw material, e.g. iron

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21
Q

Hemolytic anemias

A

Anemias associated with accelerated destruction of red cells
Classify by cause
Intrinsic, or intracorpuscular, factors
-Most inherited
*Membrane abnormalities, enzyme deficiencies, hemoglobin synthesis disorders
Extrinsic, or extracorpuscular, factors
-Acquired
*Immune mediated, mechanical destruction, infections

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22
Q

Hemolytic Anemias general features

A

Shortened red cell life span
-Premature red cell destruction
Increased rate of erythropoiesis
-Reticulocytosis
Accumulation of the products of hemoglobin catabolism
-Iron accumulation is a problem in chronic hemolytic anemias
*Iron is recycled and gut absorption is increased

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23
Q

Hemolytic Anemias

A

Extravascular hemolysis

Intravascular hemolysis

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24
Q

Extravascular hemolysis

A

Red cell destruction within the cells of the mononuclear phagocyte system
-More common mode of red cell destruction
Occurs largely within the spleen and liver
Removes damaged and immunologically targeted red cells from the circulation
Leads to
-Jaundice
-Pigment gallstones
-Haptoglobin decrease
-Reactive hyperplasia of the mononuclear phagocyte system i.e., splenomegaly

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25
Q

Intravascular hemolysis

A

Red cell destruction within the vascular space
-Less common mode
Results from
-Mechanical damage
*Defective heart valve
-Biochemical or chemical damage to the membrane
*Complement fixation, clostridial toxins, or heat
Leads to:
Hemoglobinemia
Hemoglobinuria
Hemosiderinuria
Unconjugated hyperbilirubinemia
Jaundice
Haptoglobin absence from plasma
Acute tubular necrosis in kidney, if massive hemolysis

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26
Q

Hereditary Spherocytosis

A

Inherited defect in the red cell membrane that renders the red cells spheroidal, less deformable, and vulnerable to splenic sequestration and destruction
Autosomal dominant, most common
Autosomal recessive 25% of the time, more severe form

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27
Q

Hereditary Spherocytosis

defect

A

Defect is in the membrane cytoskeleton that stabilizes the red cell membrane
-Ankyrin most common defective protein
-Band 3 next most common
-Spectrin (α and β) and band 4.2 most of remainder
Reduced membrane stability → loss of membrane fragments (but retain volume) after release into the periphery → become spherical
Spherical cells are have limited deformability → sequestered in splenic cords → destroyed by macrophages
Spleen is critical element in causing the anemia

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28
Q

Hereditary Spherocytosis

features

A 
Splenomegaly, 500-1000 g
Spherocytes in peripheral blood
Note:  Not all spherocytes are HS !!
Reticulocytosis
Erythroid hyperplasia of marrow
Hemosiderosis
Jaundice, mild
Pigment gallstones, 30-40% of adults
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29
Q

Hereditary Spherocytosis clinical

A 
Anemia
-Most moderate varies from subclinical to profound
*20-30% virtually asymptomatic
Splenomegaly
Jaundice
Generally stable
Punctuated sometimes by
-Aplastic crisis
*Parvovirus B19 infection
Hemolytic crisis
-Increased splenic sequestration and destruction
-Usually associated with an intercurrent event like infectious mononucleosis
Gallstones
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30
Q

Hereditary Spherocytosis Diagnosis

A

Family history, hematological findings, and laboratory evidence

  • Osmotic fragility test
  • Increased red cell lysis when incubated in hypotonic saline (in about 2/3 of cases)
  • MCHC increased
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31
Q

Hereditary Spherocytosis treatment

A

No specific treatment

Splenectomy can correct the anemia but not the spherocytosis

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32
Q

G6PD Deficiency epidemiology

A 
X-linked recessive
Glucose-6-phosphate dehydrogenase deficiency
-G6PD A- variant
-10% of black Americans
Protective against Plasmodium falciparum
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33
Q

G6PD Deficiency path

A

Intravascular hemolysis predominantly
-Mild component of extravascular
Decreased NADPH and glutathione
-GSH neutralizes peroxide and other reactive oxygen species
-Oxidized hemoglobin → precipitates as Heinz bodies
*Heinz bodies damage red cell membrane → hemolysis
*Heinz bodies are removed by splenic macrophages → bite cells

34
Q

G6PD A-

A

Moderately reduced half-life

Episodic hemolysis after exposure to oxidative stress

35
Q

Oxidative stresses

A

Infection—most common
Drugs
-Primaquine, chloroquine, sulfonamides

36
Q

G6PD Deficiency

clinical

A

Sudden onset of back pain with hemoglobinuria 2 to 3 days after an oxidant stress
Hemolysis is self-limited

37
Q

G6PD Deficiency

labs

A 
Normocytic anemia
Heinz bodies
-Best seen during active hemolysis
-Supravital staining
Bite cells
RBC enzyme analysis
-After hemolysis has subsided
38
Q

Sickle Cell Disease epidemiology

A 
Autosomal recessive
Most common hemoglobinopathy in black Americans
Heterozygous (Sickle cell trait, HbAS)
-No anemia
-8% of black Americans
Homozygous (Sickle cell disease, HbSS)
-Anemia
Protective against falciparum malaria
39
Q

Sickle Cell Disease path

A

Missense point mutation in β-globin gene
-Glutamic acid to valine at 6th position of β chain
HbS aggregates and polymerizes when deoxygenated
-Causes red cells to change shape (sickle or boat shape)
-Sickling is reversible initially with reoxygenation
-Repeated sickling leads to membrane damage and eventually to irreversible sickling
-Membrane damage leads to intracellular dehydration
-Sickling makes the cells “sticky”
Extravascular hemolysis predominantly of sickle cells

40
Q

Factors that affect rate and degree of sickling

A

Amount of HbS
-HbS in HbAS is too low to produce sickling or anemia
Interaction with other hemoglobins
-HbS interacts weakly with HbA
-HbF inhibits HbS polymerization
*Infants are usually 6 months old before disease manifests
-HbC (HbSC Disease) milder disease than HbSS
*2-3% of black Americans heterozygous for HbC

41
Q

Factors that affect rate and degree of sickling contin

A 
MCHC
-↑ MCHC → more sickling (membrane damage)
-↓ MCHC → less sickling (α-thalassemia)
Acidosis → more sickling
Time in low oxygen tension
-Normal capillary flow → no sickling
-Sluggish flow → more sickling
*Spleen, bone marrow
-Inflammation → more sickling
-Stickiness → more sickling
42
Q

Sickle Cell Disease clinical

A

Key processes are chronic hemolysis and tissue injury from vascular occlusion
-Extravascular hemolysis
*Irreversibly sickled cells are recognized and removed by the mononuclear phagocytes
*Minor intravascular hemolysis results from the mechanical fragility of sickled cells
Microvascular occlusion results primarily from increased adhesiveness and inflammation

43
Q

Sickle Cell Disease Crisis

A

Vaso-occlusive crises (pain crises)
Sequestration crisis
Aplastic crisis

44
Q

Vaso-occlusive crises (pain crises)

A

Episodes of hypoxic tissue injury and infarction associated with severe pain

45
Q

Sequestration crisis

A

Rapid enlargement of spleen with entrapment of red cells can result in hypovolemic shock

46
Q

Aplastic crisis

A

Transient cessation of erythropoiesis
Parvovirus B19
↓ Reticulocytes, worsening anemia

47
Q

Autosplenectomy

A

Spleen is enlarged but dysfunctional by age 2
-Howell-Jolly bodies appear
Chronic erythrostasis causes hypoxic tissue damage and fibrosis
Spleen becomes a small piece of fibrous tissue

48
Q

Increased susceptibility to infections

A

Encapsulated bacteria
-Pneumococcus, H flu
-Sepsis and meningitis are most common cause of death in children
Salmonella osteomyelitis

49
Q

Sickle cell disease

A 
Acute chest syndrome
-Vaso-occlusion of pulmonary capillaries
-Most common cause of death in adults
Dactylitis
-Painful swelling of hands and feet in infants (6-9 mo)
-Due to bone infarcts
Stroke / Seizures
Aseptic necrosis of femoral head
Leg ulcers
Calcium bilirubinate gallstones
Renal findings in HbAS and HbSS
-Microhematuria due to medulla infarcts
-Lose concentrating ability
50
Q

Sickle Cell Disease Lab

A 
Sickle cell screen
-Sodium metabisulfite reduces O2 tension, induces sickling
Hb electrophoresis
-HbAS:  HbA 55-60%, HbS 40-45%
-HbSS: HbS 90-95%, HbF 5-10%, no HbA
Peripheral Blood
-HbAS:  normal
-HbSS:  sickle cells, target cells
Prenatal screening
-Fetal DNA to detect point mutation
51
Q

Sickle Cell Disease treatment

A 
hydroxyurea
“Gentle” inhibitor of DNA synthesis
↑ HbF
↓ Leukocytes → anti-inflammatory
↑ MCV → ↓ MCHC
Nitrous oxide (NO) production
-Vasodilation
-Inhibits platelet aggregation
52
Q

Thalassemias

A

A heterogeneous group of disorders characterized by diminished globin synthesis
Epidemiology
-Autosomal recessive
-α-thalassemia in Southeast Asia, black Americans
-β-thalassemia in black Americans, Greeks, Italians

53
Q

α-Thalassemia path

A 
Decreased α-globin chain synthesis due to gene deletions
-4 genes for α-globin
-Lie in tandem on chromosome 16
Silent carrier: -One gene deletion
Asymptomatic, normal red cells
54
Q

α-thalassemia trait

A 
Two gene deletion
Mild anemia, increased RBC count
Black American type (α - / α - )
Asian type (- - / α α)
-At risk for more severe types in offspring
Labs
-Decreased MCV, Hb, Hct
-Increased RBC count
-Normal RDW, serum ferritin, Hb electrophoresis
No treatment required
55
Q

HbH (β4) disease

A

Three gene deletion
Moderately severe hemolytic anemia
-HbH is a mildly unstable hemoglobin with high oxygen affinity
-Excess β chains form inclusions that are removed by macrophages and result in the destruction of the red cells
*Also has some effect on erythroid precursors but erythropoiesis is effective
-Average Hgb is 3 g/dl less than normal controls
HbH on electrophoresis (5-30%)

56
Q

Hb Bart (γ4) disease

A

Four gene deletion
Hb Bart is a high affinity hemoglobin useless for oxygen delivery to the tissues
Intrauterine death
-Intrauterine transfusion is possible and can save some
Hb Bart on electrophoresis (>80%)
-HbH and Hb Portland

57
Q

β-Thalassemia path

A 
Mutations in β globin gene
-Promoter region
-Coding sequence
-Splice sites
Results in either
-β0  No chain synthesis
-β+  Diminished chain synthesis
58
Q

β-thalassemia minor (β/β+) [β-thal trait]

A

Mild microcytic anemia or microcytosis without anemia
Mild protection against falciparum malaria
Shortened red cell life span

59
Q

β-thalassemia minor (β/β+) [β-thal trait] labs

A 
Decreased MCV, Hb, Hct
Increased RBC count
Normal RDW, serum ferritin
Hb electrophoresis
-Decreased HbA, Increased HbA2 and HbF
60
Q

β-thalassemia major (β0/β0) [Cooley’s anemia]

A

Severe hemolytic anemia
Excess α chains precipitate
-Membrane damage and extravascular hemolysis
-Erythroid precursors undergo apoptosis (ineffective erythropoiesis)
Extramedullary hematopoiesis

61
Q

β-thalassemia major (β0/β0) [Cooley’s anemia]

labs

A 
Increased RDW, reticulocytes
Hb electrophoresis:  No HbA, Increased HbA2 and HbF
Long term transfusion requirement
-Systemic iron overload
Bone marrow transplantation
62
Q

β-Thalassemia other gene combos

A

Variable and intermediate disease

Depending on amount of β-globin produced

63
Q

Paroxysmal Nocturnal Hemoglobinuria path

A

Acquired membrane defect in multipotential myeloid stem cells
-Red cells, granulocytes, and platelets affected
-Loss of GPI anchor that complement regulatory proteins use to attach to the red cell surface
*Decay accelerating factor, CD55
*Membrane inhibitor of reactive lysis, CD59
-Cells are more susceptible to complement lysis
Intravascular complement mediated lysis of red cells, neutrophils, and platelets
-Nocturnal because acidosis enhances complement attachment to cells
*Paroxysmal and nocturnal only 25% of the time
*Chronic hemolysis without dramatic hemoglobinuria is more common

64
Q

Paroxysmal Nocturnal Hemoglobinuria clinical

A

Episodic hemoglobinuria
Increased incidence of thrombosis
Increased incidence of severe infections
Association with aplastic anemia

65
Q

Paroxysmal Nocturnal Hemoglobinuria labs

A 
Sucrose hemolysis test (sugar water test)
-Screening test
-Sugar enhances complement attachment
Acidified serum test (Ham test)
-Confirmatory test
-Activates alternative complement pathway
Peripheral Blood
-Normocytic anemia with pancytopenia
*Microcytic if iron deficiency develops
66
Q

Immune Hemolytic Anemia

A 
Extrinsic hemolytic anemias with extravascular or intravascular hemolysis
Antibodies and/or complement play a central role
Classification
Autoimmune
-Warm type
-Cold type
Drug induced
Alloimmune
67
Q

Warm Autoimmune Hemolytic Anemia

A

70% of AIHA
Primary (idiopathic) 50%
Secondary
-Leukemia, lymphoma, other neoplastic disease, autoimmune disease (esp. SLE)

68
Q

Warm Autoimmune Hemolytic Anemia path

A

IgG antibodies that react against red cell antigens coat the red cells
IgG may fix C3b to the red cells
Extravascular hemolysis
-IgG and/or C3b coated red cells are phagocytosed by macrophages in the spleen and liver

69
Q

Warm Autoimmune Hemolytic Anemia clinical & lab

A

Jaundice
Splenomegaly

Positive Direct Antiglobulin Test (DAT, Coombs’ test)
-Detects RBCs sensitized with IgG and/or C3b
Positive Indirect Antiglobulin Test (IAT, indirect Coombs’ test)
-Detects red cell reactive antibodies in the serum
Unconjugated hyperbilirubinemia
Peripheral blood
-Normocytic anemia, spherocytes may be present

70
Q

Cold Autoimmune Hemolytic Anemia

A 
30% of AIHA
Primary (idiopathic)
Secondary
-Post-infection (mycoplasma, infectious mononucleosis)
-Lymphoid neoplasms
71
Q

Cold Autoimmune Hemolytic Anemia oath

A

IgM antibodies bind red cells usually in cooler areas of the body
IgM fixes complement to the red cell
IgM dissociates at warmer temperatures in most cases
May result in intravascular hemolysis if complement is activated through to the membrane attack complex
Otherwise, extravascular hemolysis
-C3b coated cells are phagocytosed by macrophages in the liver

72
Q

Cold Autoimmune Hemolytic Anemia clinical labs

A

Hepatosplenomegaly
Raynaud’s phenomenon may result from IgM induced red cell agglutination in the cooler peripheral circulation

Positive DAT (for C3b)
If intravascular hemolysis,
-Hemoglobinuria
-Hemoglobinemia
-Decreased haptoglobin
73
Q

Drug Induced Immune Hemolytic Anemia mechanisms

A

Drug absorption
Immune complex
Autoantibody
Membrane modification

74
Q

Drug absorption

A

Penicillin

Drug absorbs onto red cells → Antibody binds drug on cell → extravascular hemolysis

75
Q

Immune complex

A

Quinidine
Drug-Antibody complexes are absorbed onto the red cells → +/- complement fixation → intravascular or extravascular hemolysis

76
Q

Autoantibody

A

α-methyldopa
Drug induces a red cell autoantibody
Indistinguishable from warm AIHA
Antibody usually disappears in several months, if drug is discontinued

77
Q

Membrane modification

A

Cephalosporins
Red cells become “sticky”
Immunoglobulin and complement components adhere non-specifically

78
Q

Angiopathic Hemolytic Anemia

A

Intravascular hemolysis due to vascular lesions causing direct mechanical damage to the red cells

79
Q

Macroangiopathic

hemolytic anemia

A

Calcified stenotic aortic valve
-Sheer forces due to turbulent flow and abnormal pressure gradients
Artificial mechanical heart valves

80
Q

Microangiopathic hemolytic anemia

A

Microvascular lesions such as fibrin or platelet thrombi damage red cells as they pass

  • Disseminated intravascular coagulation (DIC)
  • Most common cause of microangiopathic hemolytic anemia
  • Thrombotic thrombocytopenic purpura (TTP)
  • Hemolytic uremic syndrome (HUS)
  • Malignant hypertension
  • Systemic lupus erythematosus
  • Disseminated cancer
81
Q

Microangiopathic hemolytic anemia peripheral blood

A

Microangiopathic hemolysis is an important diagnostic clue rather than a major problem in and of itself
Peripheral Blood
-Red cell fragments (schistocytes)
*Helmet cells, triangle cells, burr cells

Pathology (16 decks)

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