Transcript Sickle Cell Disease

Sickle Cell
Disease
Sickle Cell Anemia
Sickle Cell anemia is an inherited red blood cell
disorder. Normal red blood cells are biconcave discs,
and they move through small blood tubes in the body
to deliver oxygen.
Sickle red blood cells become hard, sticky and shaped
like sickles. When these hard and pointed red cells go
through the small capillaries, they clog the flow and
break apart. This can cause pain, damage and a low
blood count, or anemia.
The origin of the disease is a small change in the
protein hemoglobin
A single change in an amino acid causes hemoglobin
to aggregate.
Glutamic acid is replaced by Valine in position 6 in the
beta chain.
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The replacement of valine for Glutamic acid produce
an abnormal Hb called : HbS : (2α,2βs) which is
INSOLUBLE and forms crystals when exposed to low
O2 tension : polymerizes into long fibers.
About 30% of Jamaican
patients with Sickle Cell
develop ulcers in
comparison to 1% of
Americans
Dactylitis
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Sickle cell is an autosomal recessive disease.
Therefore, the child can only get Sickle cell if both parents are
carriers, not if only one is and the other is normal. They have a
25% chance of getting it if both are carriers
Three common types of
Sickle Cell Disorders
1. Sickle Cell Anemia (Homozygous)
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Hb SS
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More common.
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Severe hemolytic anemia.
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Leg ulcers due to vascular stasis ‫ &الركود الدموي‬ischemia.
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Most Severe – No HbA
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Crises : (painful vaso-occlusive, visceral, a plastic or hemolytic)
Factors that cause crises include : infection, acidosis, dehydration,
deoxygenation, cold, exercise)
2. Double heterozygous :
(Hb SC, Hb S βthal.)
3. Sickle cell trait (Hb AS)
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Benign
No anemia
RBC remain flexible with normal morphology
Hematuria is the most common symptom
The person is a Carrier
Hb S is : 25 – 45%
Care must be taken with anesthesia, pregnancy and high altitudes.
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In Hb SS : Hb is between 6 – 9 g/dl.
The blood film show : sickle cells, target cells, Howell-Jolly bodies.
Positive Sickling test.
Hb electrophoresis :
Hb SS : 80 – 100%
no Hb A
Hb F : 5 – 15%
Howell-Jolly bodies
These are basophilic nuclear remnants
(clusters of DNA) in circulating
erythrocytes.
 They are usually observed singly in
hemolytic anemia, following
splenectomy, and in cases of splenic
atrophy.
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The Sickling Test
This is a wet preparation.
 5 drops of reagent (Sodium dithionite), are added to 1
drop of anticoagulated blood on a slide. Cover glass is
put on and sealed with petrollium jelly/parraffin wax
mixture.
 The reagent is a reducing agent.
 In Hb SS, sickling occur immediately, while it may take 1
hour in Hb S trait.
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Hb. electrophoresis
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Differentiates the various types of hemoglobins in the blood.
Electrophoresis, a process that causes movement of particles in an
electric field, resulting in formation of "bands" that separate toward one
end or the other in the field.
With the Cellulose Acetate Electrophoresis at Alkaline pH, Hb is a
negatively charged protein and when subjected to electrophoresis will
migrate toward the anode (+).
Hb S solubility Test
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This is done after the Hb electrophoresis to differentiate between
some hemoglobins that have the same electrophoretic mobility as
HbS. (Hb D & Hb G)
Only Hb S precipitate in the reduced state when placed in a high
molarity phosphate buffer.
0.05 ml of blood is added to 1 ml of the buffer and mixed in a test
tube.
Positive results : presence of Hb S : cloudy solution .
Negative results : other Hbs : clear solution .