Sickle Cell Disease (SCD) is an inherited blood
disorder that affects red blood cells. People with
SCD have red blood cells that contain mostly hemoglobin
S (S stands for Sickle), an abnormal type of hemoglobin.
Sometimes these red blood cells become sickle-shaped
(crescent-shaped) and have difficulty passing through
small blood vessels.
When sickle-shaped cells block small blood vessels,
less blood can reach that part of the body. Tissue
that does not receive a normal blood flow eventually
becomes damaged. This is what causes the complications
of SCD. There is currently no universal cure for
SCD causes chronic anemia leading to fatigue and
less endurance. Another common side effect of the
clogging is pain, which can occur anywhere in the
body. Patients with SCD are more likely to develop
infections which can become life-threatening. SCD
can also cause strokes because sickled-cells cause
the clogging of blood vessels in the head.
Hemoglobin is the main substance of the red blood
cell. It helps red blood cells carry oxygen from
the air in our lungs to all parts of the body. Normal
red blood cells contain hemoglobin A. Hemoglobin
S and hemoglobin C are abnormal types of hemoglobin.
Normal red blood cells are soft and round and can
squeeze through tiny blood tubes (vessels). Normally,
red blood cells live for about 120 days before new
ones replace them.
People with sickle cell conditions make a different
form of hemoglobin A called hemoglobin S. Red blood
cells containing mostly hemoglobin S do not live
as long as normal red blood cells (normally about
16 days). They also become stiff, distorted in shape
and have difficulty passing through the body's small
blood vessels. When sickle-shaped cells block small
blood vessels, less blood can reach that part of
the body. Tissue that does not receive a normal
blood flow eventually becomes damaged. This is what
causes the complications of SCD.
Types of SCD
There are several types of SCD. The most common
are: Sickle Cell Anemia; Sickle-Hemoglobin C Disease;
Sickle Beta-Plus Thalassemia; and Sickle Beta-Zero
What is Sickle Cell Trait?
Sickle Cell trait is an inherited condition in which
both hemoglobin A and S are produced in the red
blood cells, always more A than S. Sickle cell trait
is not a type of SCD. People with sickle cell trait
are generally healthy.
Sickle cell conditions are inherited from parents
in much the same way as blood type, hair color and
texture, eye color and other physical traits. The
types of hemoglobin a person makes in the red blood
cells depend upon what hemoglobin genes the person
inherits from his or her parents. Like most genes,
hemoglobin genes are inherited in two sets - one
from each parent.
If one parent has Sickle Cell Anemia and the other
is Normal, all of the children will have sickle
If one parent has Sickle Cell Anemia and the other
has Sickle Cell Trait, there is a 50 percent chance
of having a baby with either SCD or sickle cell
trait with each pregnancy.
When both parents have Sickle Cell Trait, they have
a 25 percent chance of having a baby with SCD with
How will I know if I have the Trait?
A simple, painless blood test, followed by a laboratory
technique called Hemoglobin Electrophoresis will
determine the type of hemoglobin you have. When
you pass an electric charge through a solution of
hemoglobin, distinct hemoglobins move different
distances, depending on their composition. This
technique differentiates between normal hemoglobin
A, Sickle hemoglobin S, and other kinds of hemoglobin
(such as C, D, E, etc.).
Sickle cells are destroyed rapidly in the body of
people with the disease causing anemia, jaundice
and the formation of gallstones.
The sickle cells also block the flow of blood through
vessels resulting in lung tissue damage (acute chest
syndrome), pain episodes (arms, legs, chest and
abdomen), stroke and priapism (painful prolonged
erection). It also causes damage to most organs
including the spleen, kidneys and liver. Damage
to the spleen makes SCD patients, especially young
children, easily overwhelmed by certain bacterial
Health maintenance for patients with SCD starts
with early diagnosis, preferably in the newborn
period and includes penicillin prophylaxis, vaccination
against pneumococcus bacteria and folic acid supplementation.
Treatment of complications often includes antibiotics,
pain management, intravenous fluids, blood transfusion
and surgery — all backed by psycho-social
support. Like all patients with chronic disease,
patients are best managed in a comprehensive multi-disciplinary
program of care.
Blood transfusions help benefit SCD patients by
reducing recurrent pain crises, risk of stroke and
other complications. Because red blood cells contain
iron, and there is no natural way for the body to
eliminate it, patients who receive repeated blood
transfusions can accumulate iron in the body until
it reaches toxic levels. It is important to remove
excess iron from the body because it can gather
in the heart, liver, or other organs and may lead
to organ damage. Treatments are available to eliminate
Promising Treatment Developments
In search for a substance that can prevent red blood
cells from sickling without causing harm to other
parts of the body, Hydroxyurea was found to reduce
the frequency of severe pain, acute chest syndrome
and the need for blood transfusions in adult patients
with SCD. Droxia, the prescription form of hydroxyurea,
was approved by the FDA in 1998 and is now available
for adult patients with sickle cell anemia. Further
research is being conducted to determine proper
treatment for children.
Other treatment options in clinical development
include new, more convenient options than current
therapies to eliminate iron overload caused by repeated
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