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Hematalogy Lecture > Test 4: Intrinsic hemolytic Anemias: Membrane Defects > Flashcards

Test 4: Intrinsic hemolytic Anemias: Membrane Defects Flashcards

1
Q

 The RBC membrane consists of two interrelated parts, the outer ______________ and the protein __________. 

A

Lipid bilayer,  Skeleton

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2
Q

Part of the RBC membrane that serves as a barrier, and separates the different concentrations from the cellular interior and the exterior blood plasma

A

Lipid bilayer

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3
Q

The protein portion of the RBC membrane is responsible for…

A

Shape, structure, deform ability, and allows for movement of ions and material between the cellular interior and the blood plasma
*alos act as receptors, RBC antigens, and enzymes

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4
Q

This is the anchor for different proteins in the plasma membrane

A

Spectrin

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5
Q

What causes anemias with high absolute reticulocyte counts?

A

-hemolysis
-acute blood loss

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6
Q

What are the different hemolysis related anemias?

A

-immune
-hemoglobinopathy
-membrane defect
-enzyme deficiency
-infection (e.g. malaria)
-microangiopathic
hemolytic anemia

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7
Q

Ture or false:

RBCs are removed from circulation after 120 days by hemolysis.

A

true

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8
Q

Where does intravascular hemolysis occur?

A

within the lumen of blood vessels

 Lysis without phagocytic involvement
 Hgb released directly into plasma

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9
Q

______________ hemolysis occurs after decrease
of RBC flexibility

 Loss of glycolytic enzymes
 Macrophages in spleen and liver (i.e., reticuloendothelial system)

A

Extravascular

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10
Q

Extravascular hemolysis:

Intramacrophage RBC breakdown occurs following phagocytosis by when the RBC is attacked by lysosomal enzymes. Hemoglobin is broken down into ______, _______, ______.

A

heme, iron, and globin

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11
Q

Extravascular Hemolysis:

Heme Iron is stored as ___________ or ________ within the macrophage until needed transferrin and cycle continues. 80% of transferrin

-Globin is broken down and returns to the amino acid pool

A

ferritin or hemosiderin

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12
Q

Intravascular or extravascular hemolysis?

Cell contents are released into the plasma.
Haptoglobin and hemopexin work to
salvage the released Hgb, so the iron is not lost.

A

Intravascular hemolysis

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13
Q

Intravascular hemolysis
Cell contents are released into the plasma.
___________ and _________ work to salvage the released Hgb, so the iron is not lost.

A

Haptoglobin and hemopexin

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14
Q

Where does haptoglobin and hemopexin carry the Hgb to?

A

to the liver to be broken down into bilirubin.

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15
Q

A decrease in serum _________ may be used
to indicate intravascular hemolysis.

A

haptoglobin

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16
Q

Intravascular hemolysis:

If haptoglonbin is depleted, free Hgb is…

A

filtered by the renal glomerulus

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17
Q

Definition of membrane defects

A

Alters the membrane’s stability, shape,
deformability, and/or permeability

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18
Q

How do membrane defects cause anemia?

A

when rate of hemolysis
surpasses the rate of compensation by
bone marrow
-Increased likelihood of being trapped in spleen

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19
Q

All hemolytic anemias can be classified into what two groups?

A

 Intrinsic hemolytic anemias
 Extrinsic hemolytic anemias

20
Q

_________ hemolytic anemias:

 Usually genetic and occur from defects in
RBC membrane, enzymes, or hemoglobin

A

Intrinsic

21
Q

_________ hemolytic anemias

 Usually are acquired and occur secondary
to a primary stimulus

A

Extrinsic

22
Q

___________ Hemolytic Anemia

RBCs themselves are defective; usually
inherited.

A

Intrinsic

23
Q

What are three sites of defect with intrinsic hemolytic anemia?

A

-membrane
-enzymes
-globin chain sequence

24
Q

Intrinsic Hemolytic Anemia:

Three examples of membrane defects?

A

 Hereditary spherocytosis (HS)
 Hereditary elliptocytosis (HE)
 Hereditary pyropoikilocytosis (HPP)

25
Q

Intrinsic Hemolytic Anemia:

Two examples of enzyme defects?

A

 G6PD deficiency
 Pyruvate kinase (PK) deficiency

26
Q

Intrinsic Hemolytic Anemia:

Examples of globin chain sequence defects?

A

 Hemoglobinopathies (Hgb SS, CC, SC, S-Thal, etc.)

27
Q

What are the peripheral blood smear findings with hemolytic anemia?

A

may include anything,
depending upon cause & degree of severity: sickled
cells, target cells, nRBCs, spherocytes, schistocytes,
parasites, & polychromasia

28
Q

RBC, Hgb, Hct Findings in Hemolytic Anemia?

A

all decreased

29
Q

MCV with hemolytic anemia?

A

Variable MCV (can be ↑ due to retic count, or ↓
due to spherocytes)

30
Q

What is the most useful in the initial evaluation with hemolytic anemia?

A

↑ retic count

31
Q

What are the urinalysis findings with hemolytic anemia?

A

↑urobilinogen in both types; but ↑ plasma
free Hgb in intravascular hemolysis

32
Q

True or false:

Positive DAT will confirm an immune hemolytic anemia

A

True

33
Q

DAT (Direct Coombs Test):

In certain diseases or conditions an individual’s blood may contain
____ antibodies that can specifically bind to antigens on the red
blood cell (RBC) surface membrane.

A

IgG

-Circulating red blood cells (RBCs) can become coated with IgG alloantibodies and/or IgG autoantibodies. Complement proteins may
subsequently bind to the bound antibodies.

34
Q

What test is used to detect antibodies or complement proteins that are bound to the surface of red blood cells?

A

direct Coombs test

35
Q

A child was seen by her physician and diagnosed with pneumonia. Her mother has brought her to the physician again because the girl’s urine began to darken after the
first visit and now is alarmingly dark. The
girl has no history of anemia, and there is no
family history. A CBC shows a mild anemia,
polychromasia, and a few schistocytes. This anemia could be categorized as:

A. Acquired, intravascular
B. Acquired, extravascular
C. Hereditary, intravascular
D. Hereditary, extravascular

A

A. Acquired, intravascular

36
Q

What are the five major sets of RBC Membrane Abnormalities?

A
  1. Hereditary Spherocytosis (HS)
  2. Hereditary Elliptocytosis (HE)
  3. Hereditary Pyropoikilocytosis (HPP)
  4. Hereditary Stomatocytosis
  5. Hereditary Xerocytosis

*NOTE: All diseases are quite heterogeneous in etiology.

37
Q

What is the prevalence of Hereditary Spherocytosis (HS)?

A

 Prevalence = about 1 in 5000 in people of Northern European (especially Scandinavian) descent are heterozygous
 Homozygous condition is not seen. (FYI: numerous
defects, usually autosomal dominant)

38
Q

Hereditary Spherocytosis (HS)?

What is the mechanism?

A

molecular defects in the membrane skeletal
proteins (spectrin, ankyrin, protein 4.1, and band 3).

- RBC p.m. buckles, defective area is removed by spleen (so some micro-spherocytes seen in peripheral blood). P.m. fluidity ↓ , & rigidity ensues, causing
eventual pre-mature hemolysis.

39
Q

Does HS automatically mean decreased MCV?

A

No!

40
Q

What is MCHC typically with Hereditary Spherocytosis?

A

MCHC ↑ in 1/2 to 2/3 of patients due to slight
cell shrinkage from dehydration.

41
Q

HS is 1st choice for condition with ↑ ______

A

MCHC (>37)

-Second choice is Sickle Cell Disease (SCD) in crisis
(due to poik) or severe burns.

42
Q

What is the confirmatory test for HS?

A

Osmotic Fragility (OF) Test

43
Q

RBCs in HS have ________ osmotic fragility. Why?

A

increased***

-reflects shape of RBCs
Spherocytes already at maximum p.m. expansion, so have limited capacity to expand in hypotonic (<
0.85% NaCl) solutions, & will lyse at higher concentrations of saline than normal RBCs would.

44
Q

Osmotic Fragility Test

 In _________ solutions, water enters the RBCs
until equilibrium is achieved, and internal volume is too great….causing hemolysis!

A

hypotonic

45
Q

What can increase the accuracy of the Osmotic fragility test?

A

Incubating the cells at 37 ̊C for 24 hours, before
testing, increases the accuracy of the test.

46
Q

Increased OF seen in HS & ____________
(cells fatter & have less resistance to
lysis).

A

stomatocytes

47
Q

Decreased osmotic fragility is seen in….

A

thalassemias, Sickle
Cell Disease, any condition with lots of
targets (cells flatter & have more resistance to lysis).

-hypochromic cells are flatter, have more room to expand

Hematalogy Lecture (35 decks)

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