Sickle cell disease

Question 1

What causes Sickle cell disorders?

Answer 1

point mutation in codon 6 of the B globin gene
this means that glutamine is substituted to valine producing Beta
meaning Hb -> HbS

Question 2

What does HbS do if exposed to low levels of oxygen for a long time?

Answer 2

polymerises and distorts the RBC membrane

Question 3

What is Sickle cell trait?

Answer 3

HbS (Bs/B0)
asymptomatic carrier trait
HbS is too low to polymerise
blood film is normal as HbA bind to each other so more of them

Question 4

When would sickle cell trait become ill?

Answer 4

low oxygen environments - altitude and general anaesthetic

Question 5

What defines sickle cell anaemia?

Answer 5

HbSS (Bs/Bs)

on blood film >80% HbS

Question 6

How does sickle cell anaemia present?

Answer 6

comes from both parents
hypersplenism due to repeated splenic infarcts
chronic haemolysis leads to short RBC lifespan
sickle crisis

Question 7

What is sickle crisis?

Answer 7

episodes of tissue infarction due to vascular occlusion

Question 8

What precipitates sickle crisis?

Answer 8

hypoxia
dehydration
infection
cold exposure
stress
fatigue

Question 9

How is sickle crisis treated?

Answer 9

opiate analgesia
rest 
hydration
oxygen
red cell exchange transfusion - get rid of HbS and replace with HbA

Question 10

What is the long term treatment of sickle cell anaemia?

Answer 10

folic acid to increase RBC turnover
hydroxycarbamide induced HbF production
for hyposplenism give prophylactic penicillin