Sickle Cell Anemia by Dr Nikhil Bansal

1. Sickle cell anaemia
Dr Nikhil Bansal
J.N.M.C.,Wardha

2. Introduction :-
 It is a haematological disorder which
results due to the inheritance of an
autosomal recessive trait.
 It results due to a single glutamic acid to
valine substitution at the position 6 of the
beta globin polypeptide chain.

3.  Homozygotes (termed SS) produce only
abnormal beta chains that make only
haemoglobin S (HbS).
 This gives rise to sickle cell anaemia.
 Heterozygotes (termed AS) produce a
mixture of normal and abnormal beta
chains making HbA and HbS both.
 This gives rise to the clinically
asymptomatic sickle trait.

4. Inheritance pattern :-
AS AS
AA AS AS SS
(Normal) (Sickle cell disease)
(Sickle cell trait)
Possible genotype of the offspring of parents with the sickle cell trait

5. Epidemoilogy:-
 This disease is profound in the mainly
central Africa, Madagascar, south-eastern
coastal areas of India , the European
nations along the Mediterranean coast like
Italy, Spain, Portugal ,Arab nations like
Oman, Saudi Arabia .

6. Pathogenesis :-
 The main role in pathogenesis is played
by the HbS.
 Deoxygenation of HbS leads to formation
of pseudocrystalline structures called
”TACTOIDS”
 These tactoids distort the red cell
membrane,thus forming sickle shaped
cells.

7.  Now ,if reoxygenation occurs, this
polymerisation is reversible.
 BUT,the distortion which has already
occurred may become irreversible.
 This leads to the formation of
“IRREVERSIBLY SICKLED” red cells.
 More the amount of HbS, more easily
occurs the formation of TACTOIDS.

8. Influence of other abnormal haemoglobins
on sickle cell polymerisation:-
 HbC participates more
readily
 HbA participates but less
readily
 HbF strongly inhibits the
process

9. Clinical features :-
 Hypoxia
 Acidosis
 Dehydration
 Infection
 Plugging of blood vessels leading to
“CRISES”

10. The “CRISES”

11. 1)Vaso – occlusive crisis :-
Plugging of small vessels in the bone
Severe bone pain
Damage to areas producing bone marrow
Tachycardia ,sweating and fever
The most common crisis

12. 2)Sickle chest syndrome :-
Follows on from a vaso–occlusive crisis
Bone marrow infarction
Fat emboli in lungs
Further infarction
Ventilatory failure
DEATH

13. 3)Sequestration crisis :-
Thrombosis of veinous outflow
Massive splenic enlargement
Hepatic sequestration with pain
Circulatory collapse
DEATH

14. 4)Aplastic crisis :-
Adult sickle cell anaemia case
Infection with parvovirus B19
Red cell aplasia (self limiting but severe)
Very low Hb count
Heart failure

15. Investigations :-
 Hb count as low as 6-8 g/dl
 Blood film
 Reticulocyte count
 Detection of the presence of HbS by
exposing the RBC’s to sodium dithionite.
 Hb electrophoresis (definitive diagnosis)

16. Management :-
 Prophylaxis with daily folic acid,
penicillin V for protection against
pneumococcal infection.
 Vaccination against pneumococcus,
haemophilus & hepatitis B.
 Vaso-occlusive crisis – aggressive
rehydration, oxygen therapy,
analgesics & antibiotics.

17.  Sequestration & aplastic crises –
transfusion of fully genotyped blood.
 Exchange transfusion of HbS with HbA.
 Administration of agents which induce
increased synthesis of HbF viz
hydroxycarbamide thus inhibiting
polymerisation of HbS.