What is Sickle Cell Disease?
Sickle cell disease is an inherited blood disorder that affects
red blood cells. People with sickle cell disease have red blood cells
that contain mostly hemoglobin* S, 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 sickle cell disease. There is currently no universal cure for
sickle cell disease.
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 (S stands for sickle). 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.
What is Sickle Cell Trait?
Sickle Cell trait (AS) 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 sickle cell disease. People with
sickle cell trait are generally healthy.
Inheritance
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.
Examples:
• If one parent has Sickle Cell Anemia and the other is Normal,
all of the children will have sickle cell trait.
• If one parent has Sickle Cell Anemia and the other has Sickle
Cell Trait, there is a 50% chance (or 1 out of 2) of having a baby
with either sickle cell disease or sickle cell trait with each pregnancy.
• When both parents have Sickle Cell Trait, they have a 25% chance
(1 of 4) of having a baby with sickle cell disease with each pregnancy.
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 hemoglobin’s move different
distances, depending on their composition. This technique differentiates
between normal hemoglobin (A), Sickle hemoglobin (S), and other
different kinds of hemoglobin (such as C, D, E, etc.).
Medical Problems
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 sickle cell disease
patients, especially young children, easily overwhelmed by certain
bacterial infections.
Treatment
Health maintenance for patients with sickle cell disease 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 psychosocial
support. Like all patients with chronic disease patients are best
managed in a comprehensive multi-disciplinary program of care.
Blood transfusions help benefit sickle cell disease 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, and other organs and may lead
to organ damage. Treatments are available to eliminate iron overload.
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 sickle
cell disease. Droxia, the prescription form of hydroxyurea, was approved
by the FDA in 1998 and is now available for adult patients with sickle
cell anemia. Studies will now be conducted to determine the proper
dosage for children.
Other treatment options in clinical development include new, more
convenient options than current therapies to eliminate iron overload
caused by repeated blood transfusions.
Copyright at 2005 Sickle Cell
Disease Association of America, Inc. 16 S. Calvert Street, Suite
600, Baltimore, Maryland 21202; 410-528-1555 Office; 410.528.1495
Fax; 800-421-8453 Toll Free; E-Mail: scdaa@sicklecelldisease.org
