Sickle Cell Anemia, Part 1 — Introduction, Incidence and Symptoms
Part 2 — Treatment, Side Effects, Restrictions, and Implications for School
What is sickle cell anemia?
Sickle cell anemia, or sickle cell disease, is an inherited disease that affects the production of hemoglobin (HEEM'-uh-gloh'-bin). Hemoglobin is the component of the red blood cells that carries oxygen from the oxygen-rich environment of the lungs to the relatively oxygen-poor environment of other body tissues. In sickle cell disease, the hemoglobin is abnormal. In the body's tissues, where the oxygen level is low, the abnormal hemoglobin sticks together to form clumps, which causes the normally disc-shaped red blood cells to become shaped like crescents or sickles. These malformed cells obstruct the small blood vessels (capillaries). This obstruction causes recurring painful episodes called sickle cell pain crises. The interrupted blood flow can cause tissue damage.
The abnormal hemoglobin that causes sickle cell anemia is called "hemoglobin S". As stated before, sickle cell anemia is an inherited disease, carried as an autosomal recessive trait. This means that both parents must carry the hemoglobin S gene, and each child would then have one chance in four of having sickle cell anemia.
Other conditions are grouped with sickle cell disease, including beta thalassemia and hemoglobin SC disease, which occur when hemoglobin S is inherited from one parent and another type of abnormal hemoglobin is inherited from the other parent. A person who inherits hemoglobin S from one parent and normal hemoglobin A from the other parent will have sickle cell trait. An individual with sickle cell trait or one of these other conditions usually will have no symptoms. If symptoms are present, they are likely to be very mild. Occasionally, a person with these conditions will have symptoms similar to sickle cell anemia.
The course of sickle cell anemia varies from patient to patient. The disease becomes life-threatening when damaged red blood cells break down (called a hemolytic crisis), when the spleen enlarges and traps blood cells (called a splenic sequestration crisis), or when certain infections cause the bone marrow to stop producing red blood cells (called an aplastic crisis). Some patients have repeated crises, which can damage different organs or organ systems, such as kidneys, lungs, bones, eyes, and the central nervous system. If a clot occurs in the brain, the person can suffer a stroke.
Acute painful episodes, referred to as sickle cell pain crises, are the most common complication of sickle cell disease. These crises occur when blood vessels are blocked and the organs are damaged by the reduced blood flow. The bones of the back, the long bones of legs and arms, and the chest are the areas most often affected in a pain crisis. The frequency of these crises varies considerable, from once every few years to several times each year. Each crisis will last hours to days, and may require hospitalization for treatment. Treatment generally includes measures to control pain and provide fluids, usually into a vein (intravenous or IV). Most of the disease's symptoms are caused by the physical change in the shape of the red blood cells. This is often called "sickling". The sickled cells are rigid and fragile and cannot fit through the smallest blood vessels in the body (capillaries). The misshaped red cells are then removed and destroyed by the spleen. Dehydration, infection and low oxygen levels increase the sickling of red blood cells. For these reasons, IV fluid therapy and oxygen are important parts of treatment.
Sickle cell anemia is usually diagnosed at birth by a special blood test, which is both routinely performed and legally required in all states. Additionally, sickle cell disease can now be diagnosed before birth, as early as the first trimester, by a procedure known as chronic villus sampling.
Incidence and prevalence
Sickle cell disease is much more common in certain ethnic groups. It is believed that this genetically different hemoglobin evolved as a protection against malaria, because an individual with sickle trait is more likely to survive an outbreak of malaria than someone with normal hemoglobin. Therefore, in those geographic areas where malaria is endemic, those with sickle cell trait were more likely to pass their genes on to their children. Sickle cell trait is found more commonly among people of African decent, but also Portuguese, Spanish, French Corsicans, Sardinians, Sicilians, mainland Italians, Greeks, Turks and Cypriots. Among African Americans, approximately one person out of every 500 is affected by sickle cell disease, and about 8 percent, or one person in 12, has sickle cell trait.
Symptoms vary greatly from person to person, but typical symptoms include:
- hand and foot pain
- joint and bone pain
- frequent infections
- abdominal pain
- chest pain
- shortness of breath
- rapid heart rate
- ulcers on lower legs
- delayed growth
- delayed puberty
- excessive thirst
- excessive urination
- bloody urine
- poor eyesight
- priapism (PREYE'-uh-piz-uhm), an unwanted, painful erection
Patients with sickle cell anemia may appear pale and tired, and there may be a noticeable yellowness in the eyes or skin. Crises can be induced by infection, exposure to extreme heat or cold, trauma to the body, dehydration and excessive physical exertion.
For more information
Part 2 — Treatment, Side Effects, Restrictions, and Implications for School
The Sickle Cell Disease Association of America, Inc.
Sickle Cell Disease Association of America, Inc.
Uriel Owens Chapter, Kansas City, Kansas
Sickle Cell Information Center
Mukta Kumar, MD
Division of Pediatric Hematology and Oncology
Department of Pediatrics
University of Kansas Medical Center
Kathy Davis, MSEd, PhD
Project Director, Connected Kansas Kids
Director, KU Kids Healing Place
University of Kansas Medical Center
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The sickle cell disease is an inherited blood
disorder that affects red blood cells. People with
sickle cell have red blood cells that have mostly
hemoglobin's, Sometimes these red blood cells
become sickle-shaped or crescent shaped and
have trouble going through small blood vessels.
When sickle-shaped cells block small blood
vessels, less blood can get to that part of the
body. Tissue that does not get a normal blood
flow eventually becomes damaged.This is what
causes the problems of sickle cell disease.As to
this day there is really no cure for sickle cell
disease.Red blood cells take oxygen from the air
we breathe into our lungs to all parts of the body.
Oxygen is carried in red blood cells by a
substance called hemoglobin(Hemoglobin â“ 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.Oxygen is carried in red blood cells
by a substance called hemoglobin.The main
hemoglobin in normal red blood cells is
hemoglobin A. 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 get to 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 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. Sickle Cell trait (AS) is
an inherited condition in which both hemoglobin A
and S are made in the red blood cells, there are
always more A than S. Sickle cell trait is not a
type of sickle cell disease. 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 things. 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 setsâ¦one
from each parent(Ex. If one parent has Sickle Cell
Anemia and the other is Normal, all of the children
will have sickle cell trait. 4 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 DO YOU KNOW IF YOU
HAVE THIS 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,).
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. 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. Hydroxyurea is a
well-known drug, however its use in sickle cell
disease is relatively new and must be approached
with caution. Short-term side effects must be
carefully monitored and long-term effects are still
unknown POTENTIAL SAVINGS FROM USE
OF HYDROXYUREA Estimated total U.S.
sickle cell patients 65,000. Percent with severe
pain 3-5 times per year 5.2%. Estimated number
with frequent severe pain 3,380. Assuming the
average annual number of episodes 4. The total
number of severe pain episodes in these patients
13,520. Assuming that 50% episodes result in
hospitalization 6,760 . Assuming the average days
of hospitalization 5 . Estimated total number of
hospital days for these patients 33,800. Assuming
cost per day $800. Total hospitalization costs for
these patients $27,040,000. Potential savings from
use of hydroxyurea in these patients in one year
$13,520,000. Estimates of sickle cell disease
patients in the U.S. is now over 70,000. In the US
there were approximately 65,000
African-Americans suffering from sickle-cell
disease. There were about 5,500 British sufferers.
Worldwide, 100,000 babies are born with the
disease annually. Sickle cell anemia results when a
person inherits two genes for sickle hemoglobin,
and is homozygous for the mutation.
American-Africans are the most likly to develope
sickle cell anemia. Hemoglobin is composed of
two pairs of peptide chains: two alpha chains and
two beta chains. Sickle hemoglobin results from a
point mutation in the beta-globin gene. This single
nucleotide change produces a single amino acid
change: a glutamic acid at position 6 has been
changed to a valine, according to the following
schedule. COOH CH - (CH2)2-COOH Glutamic
acid / NH2 COOH CH3 | CH - CH-CH3 Valine
/ NH2 Glutamic acid is, as the name says, an
acidic amino acid, which means it will have a
negative charge under normal body conditions and
thus likes to be surrounded by water molecules.
Valine, on the other hand, is a neutral, or
uncharged, amino acid. Under normal conditions it
behaves like a hydrophobic, organic molecule and
wants to hide from water. This difference makes
the globin chains of hemoglobin fold differently,
especially in the absence of oxygen. Normal
hemoglobin just gives up its oxygen when it gets to
the tissue that needs it, but it retains its shape.
Sickle hemoglobin, on the other hand, loses its
oxygen, and becomes relatively insoluble. In the
deoxygenated form, it forms into long arrays that
come out the shape of the red cell and produce
the characteristic sickling that characterizes the
disease. The insolubility of deoxygenated
(reduced) sickle hemoglobin is the basis of two
rapid diagnostic laboratory tests for sickle cell
anemia. Scientists recently have had some limited
success in using genetic engineering techniques to
get good copies of the beta globin gene into
people with sickle cell anemia. If they can succeed
in this endeavor, people with the disease may be
cured but will still be able to pass the genes onto
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