Sickle and thrombosis. The lifespan of a normal

Sickle cell disease (SCD) is an autosomal recessive
disorder, that causes a mutation of GAG -> GTG glutamine to valine at the
sixth position of the ?-globin chain of haemoglobin A (HBA), which consequently
mutates into haemoglobin S (HbS) (
SCD occurs when an offspring inherits abnormal haemoglobin S gene from both
parents. The parents of an individual with an autosomal recessive condition,
carry either one or two copies of the mutated gene known as the sickle cell
trait; however, the carrier typically doesn’t show any signs and symptoms of
the disorder. Manifestation of SCD arises due to HbS polymerising under
deoxygenated environment as HbS attaches to ? globin molecules, resulting in
highly ordered molecular polymers causing red blood cells to deform into
crescent shape. Deformed RBC cause clinical complications as cells can stick to
vessel walls thus, obstructing blood flow causing painful vaso-occlusive
complications, stroke, avascular necrosis, pulmonary hypertension, infections,
renal failure, and thrombosis. The lifespan of a normal red blood cell is
90-120 days however sickled cells prematurely break within 10-20 days leading
to increased haemolysis and anaemia consequently deteriorating individual’s

There are many research conducted to find a definite cure of
SCD; however, there are several treatments for SCD which involves the manging
the clinical complications of the condition, this includes management of pain
episodes and provide specific treatments for acute complications.

Individuals whom are affected by SCD are prone to
infections; infections are a major cause of morality and casualty in SCD,
particularly in children due to their immunologic response. Hence, children and
adults are given antibiotics (Penicillin Prophylaxis) to inhibit infections.
Young children are probable to infections which are triggered by encapsulated
organisms such as Streptococcus pneumonia and Haemophilus influenzae, while older
children and adults are affected by gram-negative enteric organisms such as
Escherichia coli, Chlamydia/Mycoplasma pneumoniae and are prone to kidney
infections, and osteomyelitis.
Prior to the use of penicillin in SCD, such infections posed as a threat within
patients as the prognosis of infection developed rapidly resulting in death
within few hours after onset. Children begin taking antibiotic penicillin when
they’re about 2 months old until they are 5 years old due to decreased ability
to produce immunological response; beforehand children under 5 years old were
probable to infections, 3.2 to 6.9 events occurred per 100 patient years but
the advancement of antibiotic treatment in SCD for children under 5 years old,
the incidence of infections associated with Streptococcus pneumonia and
meningitis has significantly decreased to 1.5 events per 100 patient years. (

Blood transfusion is used as a treatment to handle specific
episodes or used as a chronic transfusion therapy to prevent complication
linked to SCD. The benefit of blood transfusion in SCD is to increase the
oxygen- carrying capacity of the red blood cells which, decreases blood
viscosity. This will reduce the sickling of the red blood cells. Patients with
SCD blood are provided with a simple transfusion or exchange transfusion.
Simple aims to support patients whom are affected with acute anaemia; administered
packed RBC are used when levels of haemoglobin are below 50/60 g/l or 20-30 g/l
depending on the patient’s condition. (
Exchange transfusion is used to replace sickle cells through adjusting the
haemoglobin levels which initiates an increase in blood viscosity reducing
haemolytic complications. (

Patients with SCD are susceptible to have vaso- occlusive
crisis affected by blood vessel obstruction. Hydroxyurea is an effective drug
therapy which is used to subside chronic pain; it’s a “cytotoxic and
cytoreductive antimetabolite that acts via inhibition of DNA synthesis by
inhibiting ribonucleotide reductase” (
hydroxyurea increases the production of foetal haemoglobin in red blood cells to
inhibit the formation of haemoglobin. S though altering cytoreductive effects
on neutrophils, increase the water content of RBC, able to successfully navigate
sickled cells and alter the adhesion of RBC by decreasing the manifestation of
endothelia molecules. Hydroxyurea treatment has shown a significant decrease in
rates of vaso-occlusive crisis, incidence of acute chest syndrome, stroke, organ
failure and hepatic sequestration. the treatment has resulted in a reduction of
40% mortality in individuals with SCD.




Currently Haematopoietic stem cell transfusion (HSCT) acts
as a curative treatment to treat patients with SCD. HSCT is derived from the
bone marrow, peripheral blood or the umbilical cord blood; it replaces abnormal
haematopoietic cells with normal cells initiating the production of normal
globulins. In sickle cell disease…..


 Firstly there is no
doubt that the treatment success establishes an overall survival rate of
93-100% in patients, however there are impediments in the efficacy of HSCT
therapy which requires further study to make the procedure safer


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