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Clinical Problem Solving > 4 - Sickle Cell Disease > Flashcards

4 - Sickle Cell Disease Flashcards

1
Q

Why is it difficult to bind the first oxygen to hemoglobin?

A

Hemoglobin is in its T form when oxygen is low

Remember: first drink on a night out

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2
Q

Until which age Is HbF present in the blood?

A

6 months

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3
Q

What are the 3 components of a hemoglobin molecule?

A
  1. 4 globin subunits
  2. 4 heme units
  3. 4 ferrous ions
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4
Q

Concentration of which 2 substances controls blood pH?

A
  1. H+ ions

2. CO2

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5
Q

Which 4 body parts are most commonly affected by sickle crises?

A
  1. Bone
  2. Chest
  3. Brain
  4. Kidney
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6
Q

How would you diagnose sickle cell disease in a newborn?

A

Heel prick test

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7
Q

Which component of the blood binds H+ ions?

A

Hemoglobin

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8
Q

Why is oxygen readily picked up in the lungs, but given up easily to the tissues?

A

Hemoglobin’s AFFINITY for oxygen varies dramatically over a small range of oxygen levels

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9
Q

Sickle cell disease makes the transition of hemoglobin from its T form to its R
form ___ likely.

A

Less

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10
Q

Which secondary protein structure looks like a loop?

A

Alpha helix

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11
Q

Which organ destroys most of the body’s defective red blood cells?

A

Spleen

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12
Q

Why is oxygen given to patients in a sickle cell crisis?

A

Increased oxygen encourages hemoglobin to adopt its R form, reducing polymerisation

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13
Q

Compare the partial pressure of oxygen in the lungs and the tissues.

A

Lungs: higher
Tissues: lower

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14
Q

What is the secondary structure of a protein?

A

Local spatial arrangement of polypeptide backbone

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15
Q

Which component of proteins determines their tertiary structure?

A

R groups

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16
Q

Compare the symptoms of sickle cell trait and sickle cell disease.

A

Trait: asymptomatic
Disease: symptomatic; hemolysis, vaso-occlusion

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17
Q

In sickle cell patients, anemia does not have a huge impact on their quality of life. List 2 reasons why.

A
  1. It’s easier for hemoglobin to GIVE UP oxygen to tissues in its T state
  2. Increased PUMPING of blood helps compensate for low amounts of hemoglobin
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18
Q

2 carriers for sickle cell disease have a child. What is the chance that the child will have the disease?

A

1 in 4

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19
Q

Describe the process by which sickle cell disease causes cells to deform.

A

Hemoglobin polymerizes in its T form ->
Repeated oxygenation/deoxygenation cycles causes repeated distortions ->
Cells eventually stiffen and remain distorted

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20
Q

What percentage of Africans are carriers for sickle cell disease?

A

25%

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21
Q

Why might patients with sickle cell disease experience pain?

A

Vaso-occlusion of capillaries by stiff RBCs blocks blood flow, causing ischemia and infarction of downstream tissue

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22
Q

List 2 consequences of high bilirubin production.

A
  1. Jaundice

2. Gallstones

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23
Q

Why do RBC have a shortened life in sickle cell disease?

A

Repeated cycles of hemoglobin distortion weakens RBC

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24
Q

Describe the process by which a sickle crisis arises.

A

RBC must distort to fit through the capillaries ->
Sickled cells do not distort ->
Block the capillaries ->
Infarction of downstream tissues

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25
Q

The HbS mutation is found on which protein subunits?

A

Beta

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26
Q

The sickling process in general terms results in 2 broad consequences. What are these?

A
  1. Hemolysis (shorter RBC lifespan -> hemolytic)

2. Vaso-occlusion (RBC stiffness -> blocking of capillaries)

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27
Q

Compare ischemia and infarction.

A

Ischemia: obstructed blood flow; tissue still alive
Infarction: obstructed blood flow; tissue dead

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28
Q

What are the two forms of hemoglobin?

A
  1. R

2. T

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29
Q

How does a slightly reduced negative charge lead to a sickled shape in RBC?

A

Molecules in tense form polymerise

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30
Q

What is the result of imbalance between RBC production and loss in sickle cell disease?

31
Q

Which component of the blood is responsible for transporting oxygen?

A

Hemoglobin

32
Q

Compare the genotype for sickle cell trait and sickle cell disease.

A

Trait: HbAS
Disease: HbSS

33
Q

What form of hemoglobin exists in low oxygen environments?

34
Q

What form of hemoglobin exists in high oxygen environments?

35
Q

Which form of hemoglobin binds oxygen?

R

A

Remember: RELAXED, loves to bind oxygen

36
Q

Which amino acid mutation causes sickle cell disease?

A

Glutamic Acid -> Valine

37
Q

What type of subunits are there in normal adult hemoglobin, and how many are there of each type?

A

2 alpha

2 beta

38
Q

Why has sickle cell trait persisted in some populations?

A

Carrier status helps protect against malaria

39
Q

What is the inheritance pattern for sickle cell disease?

A

Autosomal recessive

40
Q

List 2 advantages conferred by the biconcave shape of normal RBC.

A
  1. More flexible

2. Increased surface area for oxygen uptake

41
Q

Which base pair mutation causes sickle cell disease?

A

Adenine -> Thymine

42
Q

What is the quaternary structure of a protein?

A

Arrangement of multiple tertiary structures

43
Q

Sickle cell disease gives hemoglobin a slightly reduced affinity for oxygen. How would this present on an oxygen dissociation curve?

A

Right shift

44
Q

In sickle cell disease, a valine replaces a glutamic acid in the beta chain. How does this affect the charge of the molecule?

A

Slightly reduced negative charge

45
Q

The core function of hemoglobin is the transport of O2 and ___.

46
Q

List 4 factors that decrease hemoglobin’s affinity for oxygen (i.e., right shift).

A
  1. Increased CO2
  2. Increased H+
  3. Increased 2,3-DPG
  4. Increased temperature
    Remember: Isabel Chang Has 2 Tits
47
Q

What is splenomegaly?

A

Abnormal enlargement of the spleen

48
Q

How does the subunit structure of the hemoglobin in a person with sickle cell disease differ from normal adult hemoglobin?

A

A beta subunit is replaced with a defective unit

49
Q

Which form of hemoglobin gives up oxygen?

T

A

Remember: TENSE, does not want to bind oxygen

50
Q

What is the average lifespan of an RBC?

51
Q

List 4 factors that increase hemoglobin’s affinity for oxygen (i.e., left shift).

A
  1. Decreased CO2
  2. Decreased H+
  3. Decreased 2,3-DPG
  4. Decreased temperature
    Remember: Drew Carey Has 2 Testicles
52
Q

What is hematopoiesis?

A

The process by which blood cells are formed

53
Q

Why does it get progressively easier to bind oxygen to hemoglobin?

A

Hemoglobin transitions to its R form as oxygen increases

Remember: additional drinks on a night out

54
Q

What is the definitive diagnostic test for HbS?

A

Hb electrophoresis

55
Q

The definitive diagnostic test for HbS is by Hb electrophoresis, which plots out different hemoglobins. However, in an urgent situation, there is a rapid bedside screening test (Sickledex) which uses a solubility method. What are the limitations of this test?

A

Cannot differentiate between sickle cell trait (HbAS) and sickle cell disease (HbSS)

56
Q

What is the tertiary structure of a protein?

A

Its three-dimensional shape

57
Q

Which component of proteins determines their secondary structure?

A

Amino acids

58
Q

What are the 2 most common secondary protein structures?

A
  1. Alpha helix

2. Beta-pleated sheet

59
Q

List 4 clinical sequalae of sickle cell disease.

A
  1. Sickle crises
  2. Infections
  3. Splenomegaly
  4. Jaundice
60
Q

What is the secondary structure of collagen?

A

Triple helix

61
Q

Where are RBC produced?

A

Bone marrow

62
Q

List 5 triggers that increase cell sickling.

A
  1. Low oxygen
  2. Dehydration
  3. Cold
  4. Infection
  5. Acid blood
63
Q

What is the shape of the hemoglobin dissociation curve?

64
Q

Which secondary protein structure looks like a plane with many folds?

A

Beta-pleated sheet

65
Q

List 4 treatments for a sickle crisis.

A
  1. Oxygen
  2. Antibiotics
  3. Painkillers
  4. Fluids
66
Q

Which organ conjugates and excretes bilirubin?

67
Q

What is the primary structure of a protein?

A

A linear sequence of amino acids

68
Q

Which component of hemoglobin binds oxygen?

69
Q

What is the only cure for sickle cell disease?

A

Bone marrow transplant

70
Q

There are many different abnormal hemoglobins. What is the name given to the hemoglobinopathy suffered by people living around the Mediterranean basin?

A

Thalassemia

71
Q

What causes jaundice?

A

Accumulation of bilirubin in the blood

72
Q

What are 2 symptoms of infarction?

A
  1. Pain

2. Fever

73
Q

Define infarction.

A

Tissue death caused by inadequate blood supply

Clinical Problem Solving (10 decks)

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