Haemolobinopathies

Question 1

What are haemoblobinopathies?

Answer 1

These are varients in the hemoglobn structure (usually single aa substitutions, but in some cases a longer or shorter globin chain)

Question 2

How are the different varients classified?

Answer 2

By a letter of the alphabet or by the place of discovery

Question 3

Describe the varient HbS

Which regions is it present in?

Answer 3

This is sickle cell Hb, present in sub-Saharan Africa, Mediterrabean and Middle East

Question 4

Where are the following varients found

• HbC
• HbE

Answer 4

HbC is common in West Africa and parts of the Mediterranean

HbE is common in India, Myanmar and South East Asia

Question 5

Describe the evidence that HbS in the heteroygous form conferred resistance against malaria

Answer 5

Lower incidence of parasitemia; When parasitemia was present these patients had a lower parasite count.

Data shows that there is a higher frequency of people with HbS trait in regions where Malaria is endemic

Question 6

What controls the frequncy of the HbS trait?

Answer 6

Two opposing selective pressures

• against homozygosity of HbS (severe anemia)
• against normal RBCs - which are highly susceptible to Malaria