Sickle Cell Anaemia

Question 1

What are the 7 objective signs of Anemia?

Answer 1

Question 2

What are the 8 subjective symptoms of anemia?

Answer 2

Question 3

Draw a table outlining types of anemia in terms of their size as visible on a MCV result.

Include mechanism and potenial causes/pathologies

Answer 3

Question 4

What are the four types of hemoglobin and what are their constituent protein chains?

Answer 4

HbA: 2 x a, 2 x b (Normal)

HbA2: 2 x a, 2 x d (less than 5%)

HbS: 2 x a, 2 x abnormal b (Sickle Cell)

HbF: 2 x a, 2 x g (Foetal, highest affinity for O2)

Question 5

Explain the sickle-like shape in terms of genetic mutation

(4 steps)

Answer 5

1. There is a single base-substitution at the 6th Codon of the beta globin gene, in which Adenine is Replaced by Thymine

2. This causes a mutation of the beta globin gene, and in subsequent protein synthesis of the beta-chains, Glutamate is replaced by Valine

3. Unlike Glutamate, Valine is non-polar and therefore hydrophobic - altering the shape of the beta chains

4. This leads to polymerization of HbS chains leading to Sickle Shape

Question 6

Name three physiological states in which HbS polymerization is encouraged.

Answer 6

1. Hypoxia (Increased Deoxy HbS)
2. Dehydration (More concentrated HbS)
3. Acidosis

Question 7

What are the two main damaging outcomes of the sickle shape upon the circulatory system?

Answer 7

1. Decreased cell lifespan from 120 days to 20-40 days
2. Vaso-Occlusive Crises

Question 8

Outline and discuss the differing outcomes for those with with Sickle Cell Trait and those with Sickle Cell D**isease

Answer 8

Sickle Cell Trait

1 normal b-chain gene, 1 mutated gene

Normally asymptomatic unless is in highly stimulatory context

55% HbA, 45% HbS is produced

Sickle Cell Disease

2 mutated b-chain genes

Only HbS is produced

Question 9

There are 11 examples of symptoms and morbidites that can present as a result of sickle cell, how many can you name?

Answer 9

+ Dactylitis

Question 10

Explain acute chest syndrome

Answer 10

Vasoocclusion leads to blockage in our microvasculature

Often precipitated by a lung infection (pneumonia)

The resulting inflammation and loss of oxygen saturation leads to further sickling of red cells

Pulmonary and systemic hypoxemia is thereby exacerbated

Question 11

Define dactylitis

Answer 11

Swelling of the veins in the hands and feet owing to vaso-occlusive infarction