Case Study: Sickle Cell Disease

Question 1

How prevalent is sickle cell disease? Identify why the risk of developing sickle cell is higher in certain populations.

Answer 1

7% of human population carriers of hemoglobin mutation . Malarial protection.

Question 2

What tests are used to diagnose sickle cell disease?

Answer 2

Universal hemoglobin screening with electrophoresis and others.

Question 3

Why might a patient with SCD be jaundiced?

Answer 3

Accumulation of heme degradation product bilirubin.

Question 4

What category does Valine (Val) fall under?

Answer 4

Hydrophobic.

Question 5

What category does Glutamic Acid (Glu) fall under?

Answer 5

Acidic.

Question 6

What is the amino acid substitution that causes SCD?

Answer 6

Glutamic acid is substituted for Valine, a hydrophobic amino acid.

Question 7

What are the probabilities of an affected adult passing the disease to their offspring?

Answer 7

If both parents are heterozygous, 25% chance of child being affected. If one is homozygous and the other heterozygous, 50% chance. If both homozygous, 100% chance. Autosomal recessive genetic disease.

Question 8

Potential treatments for SCD?

Answer 8

1. Hydroxyurea - maintains HbF (downfall it is carcinogenic)
2. Penicillin - spleen is absent or nonfunctional thus immune system is compromised.
3. Blood transfusions - successful if bring HbS down to 30% of total RBC’s. This also suppresses endogenous erythropoeisis. Careful for iron overload.
4. Cure is bone marrow transplant. Difficult to receive bone marrow.