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. 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.
Types of Sickle
Cell Disease
There are several types of sickle
cell disease. The most common are: Sickle Cell Anemia (SS),
Sickle-Hemoglobin C Disease (SC)
Sickle Beta-Plus Thalassemia and Sickle Beta-Zero Thalassemia.
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 hemoglobins
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.
|
