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

11) Hemolytic anemia—membrane & enzyme disorders Flashcards

(75 cards)

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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
SDS-PAGE can be used to...
determine which membrane protein is deficient
26
incidence is 1:4000 worldwide
hereditary ovalocytosis
27
3 phenotypes of HO/HE
- common HE - spherocytic HE - stomatocytic HE (southeast asian)
28
principle defect involves horizontal interactions in membrane spectrin, band 4.1, or integral protein defects
hereditary ovalocytosis
29
----% of patient with HE show no signs of anemia because ovalocytes have a normal lifespan and BM can compensate for mild anemia
90
30
most severe form of hereditary ovalocytosis
hereditary pyropoikilocytosis (HPP) subtype
31
HPP involves 2 ------- defects, one from each parent
spectrin
32
RBC membrane fragments when heated to 45° for 15 min (usually happens at 49°)
HPP
33
HPP on PB
- striking, bizarre micropoik - RBC budding - fragments - microspherocytes - few ovalocytes
34
by 1-2 years of age, ---------------- morphology changes to look like mild HE
poikilocytosis of infancy
35
phenotypic hybrid of hereditary spherocytosis and ovalocytosis
spherocytic HE
36
spherocytic and stomatocytic HE may be treated with...
splenectomy
37
protective against malaria and common in Melanesian pop
stomatocytic HE
38
oval cells with multiple bands across middle
stomatocytic HE
39
expression of RBC antigens is muted
stomatocytic HE
40
hemolytic HE on PB
- >25% ovalocytes, usually >60% - retic as high as 20% - bizarre poik - schistocytes - spherocytes - budding RBCs
41
explain PNH
- 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
clinical manifestations of PNH
- **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
in PNH, ---------- is due to chronic IV hemolysis, and ------------ is due to acute IV hemolysis
hemosiderinuria hemoglobinuria
44
screening test for PNH largely replaced by flow cytometry now
sucrose hemolysis test sucrose solution promotes C binding and lysis
45
confirmatory test for PNH
immunophenotyping (flow) shows lack of GPI anchored molecules (CD55 and CD59)
46
3 types of PNH based on...
amount of GPI expressed I, II, and III III = no GPI at all
47
2 disorders of membrane cation permeability
- overhydrated hereditary stomatocytosis (OHS) - dehydrated hereditary stomatocytosis (DHS)
48
RBCs are swollen (↑ net cation)
OHS
49
RBCs are dehydrated (↓ net cation)
DHS
50
AKA heredtiary xerocytosis
DHS
51
disorder of cation permeability related to Na permeability
OHS
52
disorder of cation permeability related to K permeability
DHS
53
burr cells with small projections, almost like acanthocytes
DHS
54
OHS on PB
- stomatocytes - macrocytes
55
DHS on PB
- target cells - burr cells - RBCs with Hgb concentrated on one side - few stomatocytes
56
MCHC and osmotic fragility of OHS and DHS
- OHS: ↓ MCHC, ↑ fragility - DHS: ↑ MCHC, ↓ fragility
57
tx of disorders of cation permeability
usually not necessary
58
hereditary enzyme deficiencies causing hemolytic anemia
- G6PD deficiency - PK deficiency - MR deficiency
59
RBC enzyme deficiency is suspected when...
- hemolysis is apparent - DAT= - no evidence of membrane or hgb disorder
60
ID'd in African American soldiers given primaquine in Korean war
G6PD deficiency
61
G6PD deficiency inheritance
X-linked recessive
62
G6PD is necessary for maintaining ------ in reduced state (HMS)
GSH
63
can trigger hemolysis in G6PD deficient patients
- antimalarial drugs - fava beans (favism) - moth balls - TNT
64
G6PD activity is increased in ----------, meaning...
retics high retic count may make levels seem falsely normal
65
G6PD deficiency tx
usually not indicated, except supportive during episodes
66
G6PD deficiency on PB
- normo/normo - ↑ retics - bite cells (removal of heinz bodies) - spherocytes - blister cells (RBC membrane oxidation)
67
result of RBC membrane oxidation
blister cells
68
4 tests specific for G6PD deficiency
- Heinz body test - ascorbate-cyanide test - fluorescent spot test - quantitative reduction test
69
explain fluorescent spot test
- 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
when should G6PD activity not be measured?
during acute hemolytic episodes deficient cells are sequestered and retics released have increased activity falsely normal results
71
PK deficiency results in...
a rigid, poorly deformable cell that is prematurely destroyed
72
increased 2,3-DPG less susceptible to feeling effects of anemia
PK deficiency
73
PK deficiency on PB
- normo/normo - ↑ retics - nRBCs - polychromasia - poik
74
cyanosis generally benign condition
MR deficiency
75
must distinguish MR deficiency from...
- 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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