27. Sickle-Cell Disease
Sickle-cell disease is the most common
inherited hemoglobin disorder in the United States. About 8% of
Black/African-Americans carry the sickle-hemoglobin gene. However, it
is also found in people of Arabic, Greek, Maltese, Italian, Sardinian,
Turkish, Indian, Caribbean, Latin American and Middle-Eastern descent.
In the United States, most cases of sickle-cell disease occur among
Black/African-Americans and Latino/Hispanics. About one in every 500
Black/African-Americans has sickle-cell disease.
Normally, red blood cells are round and
flexible and flow easily through blood vessels. In sickle-cell disease,
abnormal hemoglobin causes red blood cells to become stiff. Under the
microscope, they may look like the C-shaped farm tool called a sickle.
Because they are stiffer, these red blood
cells can get stuck in tiny blood vessels and cut off the blood supply
to nearby tissues. This causes a great deal of pain (called sickle-cell pain episode or sickle-cell crisis)
and may damage organs. These abnormal red blood cells die and break
down more quickly than normal red blood cells, which results in anemia.
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. Carriers of the
sickle-cell trait are usually as healthy as noncarriers. Sickle-cell
trait cannot change to become sickle-cell disease.
When two people with sickle-cell trait
have a child, there is a one-in-four chance their child may inherit two
sickle-cell genes (one gene from each parent) and have the disorder.
There is a two-in-four chance the child will have the trait. There is a
one-in-four chance 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 doesn’t, there is no chance their children will have sickle-cell disease. However, there is a 50–50 chance of each child having the trait.
Sickle-cell disease can affect biracial
children. To what degree depends on the ethnic group of each parent and
his or her genetic makeup. A union of a Caucasian and a
Black/African-American will not result in a child with sickle-cell
disease because Caucasians are not carriers of the sickle-cell gene.
However, the union of a Black/African-American and a person of
Mediterranean or Latino/Hispanic descent could result in a
child with sickle-cell disease if both parents carry the sickle-cell
gene. In addition, if both parents are biracial, they could pass the
disease to their children if each parent carries the gene. The risk of
both biracial partners being carriers is lower, but the risk is still
there and depends on each person’s genetic background and makeup.
Pregnancy and Sickle-Cell Disease
A woman with sickle-cell disease can
have a safe pregnancy. However, if you have the disease, your chances
are greater of having problems that can affect your health and your
baby’s health. During pregnancy, the disease may become more severe,
and pain episodes may be more frequent. You will need early prenatal
care and careful monitoring throughout pregnancy.
Hydroxyurea is often used to reduce the
number of pain episodes by about 50% in some severely affected adults.
At this time, we don’t recommend hydroxyurea for pregnant women.
A blood test can reveal sickle-cell
trait. There also are prenatal tests to find out if a baby will have
the disease or carry the trait. Most children with sickle-cell disease
are now identified through newborn screening tests.
28. Thalassemia
Thalassemia, also called Cooley’s anemia,
is not just one disease. It includes a number of different forms of
anemia. The thalassemia trait is found all over the world but is most
common in people from the Middle East, Greece, Italy, Georgia (the
country, not the state), Armenia, Vietnam, Laos, Thailand, Singapore,
the Philippines, Cambodia, Malaysia, Burma, Indonesia, China, East
India, Africa and Azerbaijan. It affects about 100,000 babies each year.
There are two main forms of the
disease—alpha thalassemia and beta thalassemia. The type depends on
which part of an oxygen-carrying protein (the hemoglobin) is lacking in
red blood cells. Most individuals have a mild form of the disease. The
effects of beta thalassemia can range from no effects to very severe.
A carrier of thalassemia has one normal
gene and one thalassemia gene. Having the thalassemia trait doesn’t
usually cause health problems, although women with the trait may be
more likely to develop anemia during pregnancy. Healthcare providers
may treat this with folic-acid supplementation.
When two carriers have a child, there is
a one-in-four chance their child will have a form of the disease. There
is a two-in-four chance the child will be a carrier like its parents
and a one-in-four chance the child will be completely free of the
disease. These odds are the same for each pregnancy when both parents
are carriers.
Various tests can determine whether a
person has thalassemia or is a carrier. Chorionic villus sampling (CVS)
and amniocentesis can detect thalassemia in a fetus. Early diagnosis is
important so treatment can begin at birth to prevent as many
complications as possible.
Most children born with thalassemia
appear healthy at birth, but during the first or second year of life,
they develop problems. They grow slowly and often develop jaundice.
Treatment includes frequent
blood transfusions and antibiotics. When children are treated with
transfusions to keep their hemoglobin level near normal, many
complications of thalassemia can be prevented. However, repeated blood
transfusions may lead to a buildup of iron in the body. A drug called
an iron chelator may be given to help rid the body of excess iron.
