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HEME II > Red Cell Path Ch 14 > Flashcards

Red Cell Path Ch 14 Flashcards

1
Q

Features of hemolyic anemias

A

1) premature destruction of RBCs and shortened lifespan
2) elevated erythropoitin level/erythropoisis
3) accumulation of hemoglobin degredation products

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2
Q

extravascular hemolysis

A

premature destruction of RBCs within phagocytes

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3
Q

clinical features of extravascular hemolysis

A

1) anemia
2) splenomegaly
3) jaundice

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4
Q

what is the fxn of alpha2-globulin

A

binds free hemoglobin and prevents its excretion in urine

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5
Q

intravascular hemolysis causes

A

mechanical injury, complement fixation, intracellular parasites, exogenous toxic factors

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6
Q

clinical features of intravascular hemolysis

A

1) anemia
2) hemoglobinemia
3) hemoglobinuria
4) hemosiderinuria
5) jaundice

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7
Q

hapatoglobin

A

binds free hemoglobin, produces a complex that is cleared by macrophages

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8
Q

what occurs when serum hepatoglobin is used up/depleted

A

free hemoglobin oxidizes to methemoglobin (brown in color)

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9
Q

what is true about bilirubin in uncomplicated hemolytic anemias

A

unconjugated

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10
Q

cholelithiasis

A

pigmented gallstones

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11
Q

hereditary spherocytosis (HS)

A

intrinsic defects in red cell membrane skeleton that render cells spheroid, less deformable, and vulnerable to destruction

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12
Q

where is hereditary spherocytosis prevalent

A

northern europe (1/5000); autosomal dominant 75% of time and compound heterozygosity 25%

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13
Q

spectrin components

A

2 polypeptide chains (alpha and beta) form intertwined flexible heterodimers

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14
Q

how is spectrin attached to membrane

A

1) proteins ankyrin and band 4.2 bind spectrin to transmembrane ion transporter
2) protein 4.1 binds tail of spectrin to another transmembrane protein glycophorin A

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15
Q

what is the lifespan of RBCs with HS

A

10-20 days

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16
Q

what genetic defect are most common in HS

A

ankyrin, band 3, spectrin, or band 4.2; they stabilize lipid bilayer

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17
Q

good treatment option for HS

A

splenectomy

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18
Q

red cell morphology in HS

A

small, dark-staining, lack central zone of pallor, spherocytosis

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19
Q

MCHC in HS

A

increased due to dehydration caused by loss of K+ and water

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20
Q

how often is HS asymptomatic

A

20-30%; usually compensation outpaces and mild/moderate chonic hemolytic anemia occurs

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21
Q

aplastic crisis in HS

A

generally triggered by acute parvovirus infection

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22
Q

what does parvovirus affect

A

infects and kills red cell progenitors ceasing production until immune response fixes; RBC producation back 1-2 weeks

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23
Q

what affects do red cell enzyme disfunctions have

A

reduced ability for RBCs to protect themselves against oxidative injuries and lead to hemolysis

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24
Q

Most important RBC enzyme derangement

A

glucose-6-phosphate dehydrogenase (G6PD); reduces NADP to NADPH while oxidizing glucose-6-phosphate

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25
Q

What does NADPH do in RBCs

A

converts oxidized glutathione to reduced glutathione, which protects against oxidant injury

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26
Q

How is G6PD inherited

A

X-linked

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27
Q

G6PD- is present in what ethinic group

A

10% american blacks

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28
Q

G6PD-mediterranean is present where

A

middle east

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29
Q

episodic hemolysis characteristic of G6PD

A

triggered by infections; oxygen-derived free radicals produced by leukocytes; food/drugs can also trigger (fava bean)

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30
Q

Heinz bodies morphology

A

dark inclusions within red cells stained with crystal violet

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31
Q

Heinz bodies cause

A

G6PD deficient exposed to oxidants; cross-linking of reactive sulhydryl groups on globon chains, which become denatured and form membrane bound precipitates

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32
Q

Heinz bodies effect

A

damage membrane to cause intravascular hemolysis

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33
Q

bite cells

A

phagocytes in spleen remove/’bite’ heinz bodies out of red cells

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34
Q

how long after oxidant exposure do hemolysis, anemia, hemogloburea/emia occur

A

2-3 days

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35
Q

why isn’t splenomegaly seen in G6PD abnormalities

A

hemolytic episodes are intermitent

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36
Q

sickle cell mutation

A

point mutation in 6th codon of B-globin; glutamate replaced with valine

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37
Q

How common is sickle cell

A

8-10% of african americans are heterozygous

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38
Q

Pathogenesis of sickle cell

A

HbS undergo polymerization when deoxygenated causing

1) chronic hemolysis
2) microvascular occlusions
3) tissue damage

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39
Q

variables affecting rate/degree of sickling

A

1) interaction of HbS with other types of hemoglobin
2) MCHC
3) intracellular pH
4) transit time of RBCs

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40
Q

why don’t infants become syymptomatic until 5-6 months of age

A

HbF inhibits polymizeration of HbS more than HbA

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41
Q

HbC

A

lysine substituted for glutamate in 6th aa of B-globin

42
Q

HbSC pathology

A

tend to lose salt and water and become dehydrated increasing intracellular concentration of HbS; milder than HbSS

43
Q

carrier frequency of HbC

A

2-3% american blacks heterozygous; 1/1250 have HbSC disease

44
Q

example of MCHC decrease helping reduce severity of HbS

A

HbS plus coexistant alpha-thalassemia (reduces Hb synthesis and leads to milder disease)

45
Q

Where are transit times slow in microvascular beds

A

spleen and bone marrow (also inflammation areas); increases likelyhood of sickling

46
Q

what occurs with repeated incidences of sickling in a RBC

A

dehydrated, dense, and rigid

47
Q

other properties of sickel red cells

A

express higher than normal adhesion molcules and are sticky

48
Q

What can free hemoglobin do to NO

A

bind and inactivate, enhancing vasoconstriction and platelet aggregation

49
Q

what are target cells

A

RBCs that results from dehydration

50
Q

what are howell-jolly bodies

A

small nuclear remnants; present due to asplenia

51
Q

what does bone marrow expansion cause

A

leads to bone reabsorption and secondary new bone formation, resulting in prominent cheekbones and chnges in skull that resemble a crew-cut on x-ray

52
Q

autosplenectomy

A

process of chronic erythrostasis leading to splenic infarction, fibrosis, and progressive shrinkage

53
Q

vaso-occlusive crises (pain crises)

A

episode of hypoxic injury and infarction that cause severe pain in affected region

54
Q

what are pain crises in sickle cell difficult to distinguish from in children

A

acute osteomyelitis

55
Q

acute chest syndrome

A

pain crisis in lungs (fever, cough, chest pain, pulmonary infiltrates)

56
Q

most common cause of patient morbidity and mortality in sickle cell

A

vaso-occlusive crises

57
Q

sequestration crises

A

massive entrapment of sickled cells leading to rapid spleen enlargement, hypovolemia, and sometimes shock

58
Q

aplastic crises

A

infection with parvovirus B19 which infect RBC progenitors; causes cessation of erythropoiesis

59
Q

mainstay treatment for sickle cell anemia

A

hydroxyurea (inhibitor of DNA synthesis) - increase HgF, anti-inflammatory (inhibit WBCs)

60
Q

where are alpha chain genes located from hemoglobin

A

identical pair on chromosome 16

61
Q

where are beta chain genes located from hemoglobin

A

single copy on chromosome 11

62
Q

mutations causing B-thalassemias

A

1) splicing mutation
2) promotor region mutations
3) chain terminator mutations

63
Q

Two mechanisms of anemia in B-thalssemias

A

1) deficit in HbA produces hypochromatic, microcytic RBCs 2) diminsihed survival of RBCs and their precursors due to alpha-beta imbalance

64
Q

proximal cause of red cell pathology in B-thalessemia

A

membrane damage due to imbalance btwn alpha and beta chains in HbA

65
Q

extramedullary hemotopoitic sites

A

liver, spleen, lymph nodes; sometimes thorax, abdomen, and pelvis in extreme cases

66
Q

Ineffective erythropoisis suppresses circulating levels of what, causing what?

A

hepcidin, a negative regulator of iron absorption, causing excessive absorption of dietary iron

67
Q

what is clinical classification of B-thalessemia based on

A

genetic defect (B0 B+) and gene dosage (homo vs heterozygote)

68
Q

when does anemia from B-thalassemia minor manifest

A

6-9 months after birth

69
Q

anisocytosis

A

marked variation in size

70
Q

poikilocytosis

A

marked variation in shape

71
Q

B-thalessemia histology

A

anisocytosis, poikilocytosis, microcytic, hypochromatic

72
Q

reticulocytes in B-thalessemia major

A

elevated, but lower than expected for degree of anemia due to impaired erythropoisis

73
Q

B-thalesemmia minor blood smear findings

A

hypochromia, microcytosis, basophilic stippling, target cells, mild erythroid hyperplasia in bone marrow

74
Q

gamma-globin chains in excess form

A

gamma tetramers known as hemoglobin Barts; occurs in newborns with alpha-thalsemmia

75
Q

excess B-globin chains form

A

tetramers known as HbH; occurs in older children and adults with alpha-thalassemia

76
Q

why are alpha-thalassemias less severe than B

A

gamma and beta chains more soluble and form stable tetramers

77
Q

silent carrier state

A

1/4 alpha genes deleted; barely detectable reduction in a-globin synthesis; asymptomatic, but may have microcytosis

78
Q

alpha-thalassemia trait

A

2/4 alpha genes deleted (both on one chromosome - asian, one on each chromosome - africa)clinically similar to B-thalassemia minor - microcytosis, minimal anemia

79
Q

hemoglobin H disease

A

3/4 alpha genes deleted; HgH has high affinity for O2 and prone to oxidation - precipitates out and forms intracellular inclusions that promote RBC sequestration; similar to B-thalassemia intermediate

80
Q

Hydrops fetalis

A

4/4 alpha genes deleted; fetal distress evident by 3rd trimester; infants has extreme pallor, generalized edema, massive hepatosplenomegaly; dependent on transfussions

81
Q

paroxysmal nocturnal hemoglobinuria (PNH)

A

results from aquired mutations in phosphatidylinositol glycan omplementation group A (PIGA); X-linked

82
Q

What does PIGA do

A

enzyme essential for synthesis of certain cell surface proteins

83
Q

PNH incidence

A

2 to 5 per million in US

84
Q

what is deficiency in PNH

A

GPI-linked proteins deficient because of somatic mutations that inactivate PIGA

85
Q

lyonization

A

random inactivation of one X chromosme in females

86
Q

3 proteins PNH blood cells are deficient in

A

1) decay-accelerating factor/CD55
2) membrane inhibitor of reactive lysis/CD59
3) C8 binding protein

87
Q

most important deficient protein in PNH

A

CD59; potent inhibitor of C3 convertase that prevents spontaneous activation of the alternative complement pathway

88
Q

intravascular hemolysis in PNH cause by

A

C5b-C9 membrane attack complex; paroxysmal and noctural in 25%; generally chronic hemolysis without dramatic hemoglobinuria

89
Q

why would red cells in PNH tend to lyse at night

A

slight decrease in blood pH, increases activity of complement

90
Q

leading cause of death in PNH

A

thrombosis (40%); dysfxn of platelets due to absence of certain GPI-linked proteins and absorption of NO by free hemoglobin

91
Q

immunohemolytic anemia

A

caused by antibodies that bind red cells leading to premature destruction

92
Q

how are immunohemolytic anemias classified

A

by characteristics of reponsible antibody

93
Q

warm antibody type

A

most common form of immunohemolytic anemia; 50% idiopathic; generally IgG

94
Q

drug-induced immunohemolytic anemia mechanisms

A

1) antigenic drugs - bind red cells, recognized by anti-druf antibodies
2) tolerance-breaking drugs - unknown

95
Q

cold agglutinin type

A

caused by IgM antibodies (15-30% cases); follows some infections; rarely associated with clinically significant hemolysis

96
Q

cold agglutinin type cause

A

IgM released, transient interaction with IgM deposits sublytic quantities of C3b (excellent opsonin), red cells phagocytized in liver, spleen, and bone marrow

97
Q

cold agglutinin clinical appearance

A

pallor, cyanosis, Raynaud phenomenon

98
Q

cold hemolysin type

A

autoantibodies responsible for paroxysmal cold hemoglobinuria; IgGs bind P blood group antigen on RBC surface

99
Q

most common cases of cold hemolysin type are seen

A

in children following viral infection

100
Q

most significant hemolysis caused by trauma

A

cardiac valve protheses and microangioplastic disorders

101
Q

what is hemolysis in microangioplastic disorders caused from

A

microvascular lesion that results in narrowing in lumin; generally due to deposition of fibrin and platelets

102
Q

histology of RBCs hemolysed by trauma

A

apprearance of RBC fragments (schistocytes), ‘burr’ cells, ‘helmet’ cells, and ‘triangle’ cells

HEME II (5 decks)

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