What is sickle cell
disease?
Sickle cell disease is the most common inherited blood disorder
in the United States. Approximately 80,000 Americans have the
disease.
In the United States, sickle cell disease is most prevalent among
African Americans. About one in 12 African Americans and about
one in 100 Hispanic Americans carry the sickle cell trait, which
means they are carriers of the disease.
The symptoms of sickle cell disease
are caused by abnormal hemoglobin. Hemoglobin, the main protein
inside red blood cells, carries oxygen from the lungs and takes
it to every part of the body. Normally, red blood cells are round
and flexible and flow easily through blood vessels. But in sickle
cell disease, the abnormal hemoglobin causes red blood cells to
become stiff and, under the microscope, may look like a C-shaped
farm tool called a sickle. These stiffer red blood cells can get
stuck in tiny blood vessels, cutting off the blood supply to nearby
tissues. This is what causes pain (called a sickle cell pain episode
or crisis) and sometimes organ damage in sickle cell disease.
Sickle-shaped red blood cells also die and break down more quickly
than normal red blood cells, resulting in anemia.
What medical problems
occur with sickle cell disease?
The effects of sickle cell disease vary greatly from one person
to the next. Some affected children and adults are usually healthy,
while others are frequently hospitalized. Some common problems
seen in sickle cell disease include the following:
Infections. Infants
and young children with sickle cell disease are especially vulnerable
to serious bacterial infections, such as those that cause meningitis
(infection of the lining of the brain) and blood infection. Infections
are a major cause of death in children with sickle cell disease.
But deaths have declined dramatically since doctors began routinely
treating children with sickle cell disease with the antibiotic
penicillin to help prevent these infections. Most children with
sickle cell disease are now identified through newborn screening
tests, so they can receive special medical care to help prevent
complications. More than 40 states screen newborns for sickle
cell disease. This alerts physicians to begin treatment before
dangerous infections occur.
Pain episodes.
This is the most common symptom of sickle cell disease. Some affected
individuals have one or fewer pain episodes a year, while others
may have 15 or more. Pain episodes usually last a few hours to
a few days, but they may sometimes last for weeks. Pain can occur
in any organ or joint in the body, wherever sickle-shaped cells
pile up and block blood vessels.
Hand-foot syndrome.
Hands and feet may swell when small blood vessels become blocked.
This may be the first symptom of sickle cell disease in babies,
who also may develop a fever. It usually is treated with pain
medication and fluids.
Stroke. If sickle-shaped
cells block a blood vessel in the brain, a stroke can result.
About 10 percent of children with sickle cell disease have a stroke.
This can lead to lasting disabilities, including learning problems.
Acute chest syndrome.
This is similar to pneumonia, with symptoms such as difficulty
breathing, chest pain and fever. It can be caused by an infection
or by blocked blood vessels in the lung. This potentially life-threatening
disorder should be treated in the hospital. Treatments may include
antibiotics, blood transfusions, pain medications, oxygen and
medicines that help open up blood vessels and improve breathing.
Vision problems.
When tiny blood vessels in the eye become blocked with sickle-shaped
cells, vision problems and even blindness can result. Some children
with sickle cell disease may need regular eye exams. When eye
problems occur, laser treatment often prevents further vision
loss.
Slow growth.
Children with anemia tend to grow slower than normal and enter
puberty later than other children. They also may be pale, have
shortness of breath and tire easily.
Is sickle cell trait the same thing as sickle
cell disease?
No. A person who inherits the sickle cell gene from one parent and
the normal type of that gene from the other parent is said to have
sickle cell trait. One in 12 African-Americans in this country has
sickle cell trait. Carriers of the sickle cell gene generally are
as healthy as non-carriers. Sickle cell trait cannot change to become
sickle cell disease. However, when two people with sickle cell trait
have a child, their child may inherit two sickle cell genes and
have the disorder.
What are the chances that parents with sickle cell trait will
pass it on to their children?
There is a 50 percent chance that a child born to parents who
both carry a sickle cell gene will have the trait. There is a
25 percent chance that the child will have sickle cell disease.
There also is a 25 percent chance that the child will have neither
the trait nor the disease. These chances are the same in each
pregnancy.
If only one parent has the trait and the other has no abnormal
hemoglobin gene, there is no chance that their children will have
sickle cell disease. However, there is a 50-50 chance of each
child having the trait.
Can a woman with sickle cell disease have a safe pregnancy?
Yes. However, women with sickle cell disease are at increased
risk of complications that can affect their health and that of
their babies. During pregnancy, the disease may become more severe
and pain episodes may occur more frequently. A pregnant woman
with sickle cell disease is at increased risk of preterm labor
and of having a low-birthweight baby. However, with early prenatal
care and careful monitoring throughout pregnancy, women with sickle
cell disease can have a healthy pregnancy.
Is there a test for sickle cell disease or trait?
Yes. A person can have a blood test to find out if he has either
sickle cell trait or a form of the disease. There also are prenatal
tests to find out if the baby will have the disease or carry the
trait. If both parents have the sickle cell trait, in three out
of four cases, the prenatal test will show that the baby will
not have sickle cell disease.
