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Mercy CLS 6: Hematology > 11) Hemolytic anemia—membrane & enzyme disorders > Flashcards

11) Hemolytic anemia—membrane & enzyme disorders Flashcards

1
Q

hemolytic anemia

A

the lifespan of the RBC is shortened

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2
Q

whether anemia is apparent during a hemolytic state depends on…

A

whether the BM is compensating

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3
Q

types of hemolytic anemias

A
  • intracorpuscular (intrinsic) defects—RBCs are the problem
  • extracorpuscular (extrinsic) defects—external cause for lysis
  • intravascular
  • extravascular
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4
Q

general approach to dx of hemolytic anemias

A
  1. establish ↑ RBC destruction
  2. establish ↑ RBC production
  3. establish cause of hemolysis
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5
Q

4 markers of RBC destruction

A
  • ↑ serum unconjugated bilirubin (reflects hgb catabolism)
  • ↓ haptoglobin (very sensitive but affected by other things)
  • hemoglobinemia, hemoglobinuria, or hemosiderinuria (IV hemolysis)
  • RBC survival studies
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6
Q

radioactive label used in RBC survival studies

A

chromium

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7
Q

RBC survival studies are helpful in detecting…

A

mild hemolytic anemia in which other signs of hemolysis are absent

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8
Q

retics are always —- in a hemolytic state

A

↑

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9
Q

more accurate than retic count alone, because it takes into account pt’s hct and “shift retics”

A

retic production index

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10
Q

RPI > —— indicates hemolysis or acute hemorrhage

A

3

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11
Q

RPI calculation

A

RPI = (% retics)(Hct/45)/maturation time

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12
Q

first 2 things we do to investigate cause of hemolysis

A

DAT to eliminate immune cause
PB smear to look for schistocytes, spherocytes

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13
Q

3 hereditary defects of the RBC membrane

A
  • hereditary spherocytosis
  • hereditary ovalocytosis
  • paroxysmal nocturnal hemoglobinuria
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14
Q

RBC’s ability to deform depends on 3 factors:

A
  1. membrane structure
  2. surface:volume ratio
  3. cytoplasmic vicsosity
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15
Q

affects 1/2000 northern Europeans

A

hereditary spherocytosis

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16
Q

vertical interactions between skeleton and lipid bilayer
deficiency of spectrin and ankyrin

A

hereditary spherocytosis

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17
Q

RBCs have Na+ permeability 10x greater than normal, so pumps have to work harder

A

hereditary spherocytes

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18
Q

complication of hereditary spherocytosis

A

aplastic crisis with parvovirus B19

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19
Q

prevents significant hemolysis in HS patients

A

splenectomy

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20
Q

hereditary spherocytosis lab findings

A
  • retics >8
  • MCHC >36
  • spherocytes, polychromasia
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21
Q

osmotic fragility test measures…

A

RBC’s resistance to hemolysis by osmotic stress (using solutions with gradually ↓ concentrations of NaCl)

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22
Q

HS patients’ cells lyse at —— concentrations of saline than normal control RBCs

A

higher

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23
Q

key lab finding for hereditary spherocytosis

A

↑ osmotic fragility

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24
Q

limitations of osmotic fragility

A
  • not abnormal until at least 1-2% of RBCs are spherocytes
  • mild cases may need incubation overnight at 37°
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25
Q

SDS-PAGE can be used to…

A

determine which membrane protein is deficient

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26
Q

incidence is 1:4000 worldwide

A

hereditary ovalocytosis

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27
Q

3 phenotypes of HO/HE

A
  • common HE
  • spherocytic HE
  • stomatocytic HE (southeast asian)
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28
Q

principle defect involves horizontal interactions in membrane
spectrin, band 4.1, or integral protein defects

A

hereditary ovalocytosis

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29
Q

—-% of patient with HE show no signs of anemia because ovalocytes have a normal lifespan and BM can compensate for mild anemia

A

90

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30
Q

most severe form of hereditary ovalocytosis

A

hereditary pyropoikilocytosis (HPP) subtype

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31
Q

HPP involves 2 ——- defects, one from each parent

32
Q

RBC membrane fragments when heated to 45° for 15 min (usually happens at 49°)

33
Q

HPP on PB

A
  • striking, bizarre micropoik
  • RBC budding
  • fragments
  • microspherocytes
  • few ovalocytes
34
Q

by 1-2 years of age, —————- morphology changes to look like mild HE

A

poikilocytosis of infancy

35
Q

phenotypic hybrid of hereditary spherocytosis and ovalocytosis

A

spherocytic HE

36
Q

spherocytic and stomatocytic HE may be treated with…

A

splenectomy

37
Q

protective against malaria and common in Melanesian pop

A

stomatocytic HE

38
Q

oval cells with multiple bands across middle

A

stomatocytic HE

39
Q

expression of RBC antigens is muted

A

stomatocytic HE

40
Q

hemolytic HE on PB

A
  • > 25% ovalocytes, usually >60%
  • retic as high as 20%
  • bizarre poik
  • schistocytes
  • spherocytes
  • budding RBCs
41
Q

explain PNH

A
  • acquired membrane disorder caused by stem cell mutation
  • mutation in PIGA gene
  • ↓ glycolipid GPI (anchors complement regulators DAF and MIRL, or CD55 and CD59)
  • ↑ susceptibility to complement lysis
  • oftens happens in acidic kidney environment at night
42
Q

clinical manifestations of PNH

A
  • hyperhemolysis —intermittent, acute episodes of IV hemolysis (dark urine in mornings)
  • venous thrombosis — abnormal plt function
  • infection —↓ granulocytes or abnormal function
  • bone marrow hypoplasia
43
Q

in PNH, ———- is due to chronic IV hemolysis, and ———— is due to acute IV hemolysis

A

hemosiderinuria
hemoglobinuria

44
Q

screening test for PNH largely replaced by flow cytometry now

A

sucrose hemolysis test

sucrose solution promotes C binding and lysis

45
Q

confirmatory test for PNH

A

immunophenotyping (flow)

shows lack of GPI anchored molecules (CD55 and CD59)

46
Q

3 types of PNH based on…

A

amount of GPI expressed
I, II, and III

III = no GPI at all

47
Q

2 disorders of membrane cation permeability

A
  • overhydrated hereditary stomatocytosis (OHS)
  • dehydrated hereditary stomatocytosis (DHS)
48
Q

RBCs are swollen (↑ net cation)

49
Q

RBCs are dehydrated (↓ net cation)

50
Q

AKA heredtiary xerocytosis

51
Q

disorder of cation permeability related to Na permeability

52
Q

disorder of cation permeability related to K permeability

53
Q

burr cells with small projections, almost like acanthocytes

54
Q

OHS on PB

A
  • stomatocytes
  • macrocytes
55
Q

DHS on PB

A
  • target cells
  • burr cells
  • RBCs with Hgb concentrated on one side
  • few stomatocytes
56
Q

MCHC and osmotic fragility of OHS and DHS

A
  • OHS: ↓ MCHC, ↑ fragility
  • DHS: ↑ MCHC, ↓ fragility
57
Q

tx of disorders of cation permeability

A

usually not necessary

58
Q

hereditary enzyme deficiencies causing hemolytic anemia

A
  • G6PD deficiency
  • PK deficiency
  • MR deficiency
59
Q

RBC enzyme deficiency is suspected when…

A
  • hemolysis is apparent
  • DAT=
  • no evidence of membrane or hgb disorder
60
Q

ID’d in African American soldiers given primaquine in Korean war

A

G6PD deficiency

61
Q

G6PD deficiency inheritance

A

X-linked recessive

62
Q

G6PD is necessary for maintaining —— in reduced state (HMS)

63
Q

can trigger hemolysis in G6PD deficient patients

A
  • antimalarial drugs
  • fava beans (favism)
  • moth balls
  • TNT
64
Q

G6PD activity is increased in ———-, meaning…

A

retics
high retic count may make levels seem falsely normal

65
Q

G6PD deficiency tx

A

usually not indicated, except supportive during episodes

66
Q

G6PD deficiency on PB

A
  • normo/normo
  • ↑ retics
  • bite cells (removal of heinz bodies)
  • spherocytes
  • blister cells (RBC membrane oxidation)
67
Q

result of RBC membrane oxidation

A

blister cells

68
Q

4 tests specific for G6PD deficiency

A
  • Heinz body test
  • ascorbate-cyanide test
  • fluorescent spot test
  • quantitative reduction test
69
Q

explain fluorescent spot test

A
  • NADPH fluoresces
  • if G6PD is absent, it will not convert G6P to NADH—no fluorescence
  • if PK is absent, fluorescence persists for close to an hour
70
Q

when should G6PD activity not be measured?

A

during acute hemolytic episodes

deficient cells are sequestered and retics released have increased activity
falsely normal results

71
Q

PK deficiency results in…

A

a rigid, poorly deformable cell that is prematurely destroyed

72
Q

increased 2,3-DPG
less susceptible to feeling effects of anemia

A

PK deficiency

73
Q

PK deficiency on PB

A
  • normo/normo
  • ↑ retics
  • nRBCs
  • polychromasia
  • poik
74
Q

cyanosis
generally benign condition

A

MR deficiency

75
Q

must distinguish MR deficiency from…

A
  • Hgb M disease (more susceptible to oxidize)
  • Acute reaction to various drugs

Distinguish via mHgb level, enzyme activity, Hgb electrophoresis.

Mercy CLS 6: Hematology (25 decks)

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