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RHS > L16- RBC Pathology II (Sickle Cell Disease) > Flashcards

L16- RBC Pathology II (Sickle Cell Disease) Flashcards

1
Q

define:

(1) hemoglobinopathies

(2) thalassemia syndromes

A

1- mutations in gobin genes (hereditary) –> production of defective Hb

2- mutations in globin genes (hereditary) –> dec synthesis of a globin chain of HbA (α/β)

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2
Q

describe the breakdown of Hb in adults, by %

A

HbA, α2β2, 96%
HbA2, α2δ2, 2%
HbF, α2γ2, 2%

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3
Q

describe the mutation in Sickle Cell

A

Pt mutation, replacing glutamic acid(+) with a valine(neutral)

-position 6 of β globin gene
=> HbS

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4
Q

Sickle Cell Disease:

  • (1) anemia, describe Hb genes and phenotype
  • (2) trait, describe Hb genes and phenotype
  • (3) why is it prevalent (mainly in Africa)
A

1- homozygotes, 100% HbS = SS
2- heterozygotes, 40% HbS = AS
3- protective effect against severe malarial infection

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5
Q

describe the pathogenesis of Sickle Cell disease and the effects on RBC life span

A
  • HbS molecules have inc tendency to aggregate and polymerize when deoxygenated
  • assembles into long-needle like fibers –> sickle shaped RBCs
  • at first its reversible with reoxygenation –> but repeated membrane damage (repeated episodes) –> irreversible sickling
  • inc RBC stickiness => prone to small vessel thrombosis

-RBC lifespan, 10-15 days

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6
Q

what are the factors that affect sickling in Sickle Cell Disease (hint- 4)

A

1- intracellular levels of other Hb, not HbS
2- intracellular concentration of HbS
3- acidity (low pH => inc sickling)
4- length of exposure to low O2 tension

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7
Q

explain how intracellular levels of other Hbs besides HbS affects sickling

A
  • HbA presence in HbAS = dec sickling
  • HbF presence afterbirth for 6 mos = dec sickling
  • HbC presence in HbSC = inc sicklling
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8
Q

explain how intracellular concentration of HbS affects sickling

A
  • dehydration = inc sickling

- co-existent α-thallassemia –> dec [Hb] = dec sickling

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9
Q

describe the appearance of symptoms in people with HbSA

A

(sickle cell trait)

  • usually asymptomatic
  • symptomatic during severe hypoxic states (eg. high altitude)
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10
Q

describe the appearance of symptoms in people with HbSS

A

(sickle cell disease / anemia)

  • asymptomatic for first 6 mos of life (b/c HbF presence)
  • acute or chronic Sxs
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11
Q

Sickle Cell Disease clinicopathological features:
-abnormal RBCs undergo (intra-/extra-)vascular hemolysis leading to (2)

-bone marrow will become (3) leading to (4) changes in the bones

A

1- both intra-/extravascular hemolysis
2- moderate to severe anemia

3- hyperplastic (precursor overdrive)
4- bony skull is expanded to inc bone marrow and RBC production => facial deformities

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12
Q

Sickle Cell Disease clinicopathological features:

  • (1) is the first common effect seen in the spleen of children, explain
  • (2) is the more advanced effect seen in the spleen in early adulthood, explain
  • due to (2), patients are susceptible to (3) infections

-Hb degradation leads to a (4) state in the blood, where (5) is the key risk

A

1- splenomegaly: due to RBC entrapment in pleen

2- autosplenectomy: erythrostasis –> repeated splenic infarctions / fibrosis

3- encapsulated bacteria, e.g. H. influenza, S. pneumoniae

4- hyperbilirubinemia (+ jaundice)
5- bilirubin gallstones

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13
Q

list the common triggers of sickle cell crisis

A
  • infections
  • dehydration
  • cold exposure
  • hypoxia
  • acidosis
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14
Q

list the 4 types of Sickle Cell Crises

A

1) **vaso-occlusive / painful crisis
2) sequestration crisis
3) aplastic crisis
4) hemolytic crisis

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15
Q

Describe the effects of a Vaso-occlusive crisis in the following organs:

(1) brain
(2) retina
(3) lungs
(4) kidneys
(5) legs
(6) bones
(7) penis

A

1- stroke
2- proliferative retinopathy
3- acute chest syndrome
4- renal infarctions, papillary necrosis
5- leg ulcers
6- **dactylitis, hand-foot syndrome (very common)
7- priapism, painful with unwanted erections

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16
Q

Describe the effects of a Vaso-occlusive crisis in the following organs:

(1) brain
(2) retina
(3) lungs
(4) kidneys
(5) legs
(6) bones
(7) penis

A

1- stroke
2- proliferative retinopathy
3- acute chest syndrome
4- renal infarctions, papillary necrosis
5- leg ulcers
6- **dactylitis, hand-foot syndrome (very common)
7- priapism, painful with unwanted erections

17
Q

describe the onset and effects of a sequestration crisis

A
  • in children with intact spleens

- massive entrapment of sickle RBCs –> rapid pooling of blood in spleen –> splenomegaly –> hypovolemia and or shock

18
Q

describe the onset and effects of a aplastic crisis

A
  • red Progenitor cells infected with parvovirus B19
  • -> transient cessation of erythropoiesis
  • -> sudden worsening of anemia

(self limited crisis)

19
Q

describe the onset and effects of a hemolytic crisis

A

exaggeration of hemolysis

20
Q

Complications in Sickle Cell Disease:

  • (1) CNS effects
  • (2) general effects in terms of child progression
  • (3) lung effects
  • (4) heart effects
  • (5) liver effects
A 
1- neurological deficits, seizure disorder
2- delayed puberty, stunted growth
3- pulmonary HTN
4- cardiomyopathy
5- hemochromatosis, pigmented gallstones
21
Q

Complications in Sickle Cell Disease:

  • (1) Bone effects
  • (2) Renal effects
A

1- chronic bone pains, osteoporosis, avascular necrosis, osteomyelitis

3- FSGS, papillary necrosis, renal medullary carcinoma

22
Q

Diagnosis of Sickle Cell Disease:

  • (1) non-lab findings
  • (2) blood findings
  • (3) special/specific tests
A

1- clinical Sxs w/ FHx

2- CBC for anemia, hemolytic evidence, Peripheral blood findings: sickled cells, polychromatic cells +/- nucleus, Howell-Jolly bodies (post-autosplenectomy)

3- Sickling Test, Hb electrophoresis

23
Q

Sickling test is a (diagnostic/screening) SCD test that involves doing (2)

A

1- screening

2- mixing blood w/ oxgen-consuming agent (metabisulfite) –> induces sickling

24
Q

Hb electrophoresis is a (diagnostic/screening) SCD test that will have (2) result for sickle cell anemia and (3) result for sickle cell trait

A

1- diagnostic
2- (anemia) HbS, HbF present – NO HbA
3- (trait) HbS, HbF, HbA all present

25
Q

_____ can be done prenatally to test for SCD

A

-DNA screening

26
Q

list the 5 common treatments for sickle cell disease

A

-support therapy in crises: anagelsics, rehydration, exchange transfusions

  • B9 supplements
  • Penicillin prophylaxis
  • Hydroxyurea (inc [HbF], inhibits HbS polymerization)

-bone marrow transplants

27
Q

Sickle Cell Disease (HbSS) outcomes:

  • (1) survival rate at 20 y/o
  • (2) survival rate at 50 y/o
  • (3) major cause of death in children <5 y/o
  • (4) are serious complications, worse with recurrences
  • (5) adults may develop these manifestations
A 
1- 90%
2- 50%
3- infections
4- acute chest syndrome, stroke, kidney damage are serious Vaso-occlusive complications
5- organ failure (e.g. kidneys)

RHS (35 decks)

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