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HAEMOGLOBINOPATHIES, SICKLE CELL ANAEMIA - Coggle Diagram
HAEMOGLOBINOPATHIES
Sickle syndromes
- Presence of
sickle haemoglobin (HbS) in RBC
- HbS develop sickling
when exposed to low O2 tension
- Highest frequency in
blacks and central Africa
- Patients of HbS are
relatively protected against
falciparum (malaria)
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SICKLE CELL ANAEMIA
PATHOGENESIS
1.Basic molecular lesion
- HbS: single point mutation in one
amino acid out of 146 in Hb
molecule. Subsitution of valine for
glutamic acid producing Hb a2b2
- In deoxygenation, HbS containing
RBC change to elongated crescent
shaped or sickle shaped cells.
Polymerization of deoxygenated
HbS which aggregates to form
elongated rod-like polymers
- Reversible – irreversible sickling
- Oxygen dependant sickling is
usually reversible, but damage to
cell membrane leads to irreversibly
sickled red cells
- Factors determining rate of
sickling
- Presence of non-HbS haemoglobins:
HbA readily participates in
co-polymerization
- Intracellular concentration of HbS
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CLINICAL FEATURES
- Widespread clinical features
- Symptoms appear after 6 months of life
- severe chronic hemolytic anaemia
- Vaso-occlusive phenomena :
- recurrent occlusions
due to obstruction by sickled cells upon deoxygenatin or dehydration
a. Micro infarcts:
- abdomen,
- chest,
- back,
- joints,
- recurrent painful crisis
b. Macro infarcts:
- spleen,
- bone marrow,
- bones,
- lungs,
- kidneys,
- CNS,
- retina,
- skin
- Constitutional symptoms :
- impaired growth and development,
- frequent susceptibility to infection
- Sickle cell anaemia (SS)
is a homozygous state of HbS
- Abnormal gene inherited from each parent
- SS is a severe disorder with protean clinical manifestations and decreased life expectancy