Medical Information
What is hemophilia?
Hemophilia is a rare
genetic bleeding disorder that almost always occurs in
males. A person has hemophilia when he or she inherits problems with certain
blood
clotting factors, making them unable to work properly.
Blood-clotting factors are needed to help stop bleeding after a cut or injury
and to prevent spontaneous bleeding.
The hemophilia gene can contain many different errors, leading to
different degrees of abnormality in the amount of clotting factor produced. A
person with hemophilia often needs treatment to prevent severe blood loss and
stop internal bleeding.
There are two major types of hemophilia, although the symptoms
are the same.
- Hemophilia A is caused
by a deficiency of active clotting factor VIII (8). Approximately 1 out of
every 5,000 male babies is born with hemophilia A.1
- Hemophilia B (Christmas
disease) is caused by a lack of active clotting factor IX (9). It is less
common, occurring in 1 out of every 30,000 male babies.1
Hemophilia is usually classified by how severe it is. There are
three levels of hemophilia, although they can overlap. The severity of the
disease is defined by how much clotting factor is produced and in what
situations bleeding most often occurs.
- Mild hemophilia:
Clotting factor VIII or clotting factor IX level is 5% of normal or greater.
Mild hemophilia might not be recognized unless there is excessive bleeding
after a major injury or surgery.
- Moderate hemophilia: Clotting factor
VIII or clotting factor IX level is 1% to 5% of normal. Bleeding usually
follows a fall, sprain, or strain.
- Severe hemophilia: Clotting factor VIII or clotting factor IX level is less
than 1% of normal. Bleeding often happens one or more times a week for no
apparent reason (spontaneously).
The percentage of clotting factors stays about the same
throughout a person's life. All family members who have hemophilia usually will
have similar forms.
In very rare cases, a person develops a form of hemophilia,
called acquired hemophilia, that is not inherited. If you have acquired
hemophilia, your clotting factors don't work properly because your body makes
antibodies that attack them.
What is clotting factor replacement therapy for hemophilia?
Clotting factor concentrates can help control bleeding
in people with hemophilia by helping blood to clot properly. They do not cure
hemophilia or repair damage that may have already occurred, such as
inflammation from repeated episodes of bleeding in the joints. The severity of
hemophilia, the location of the bleeding, and how much bleeding has already
occurred often determines how much clotting factor concentrate is given.
In the United States, blood products are carefully screened.
Blood that is suspected of being contaminated with a virus, such as the
human immunodeficiency virus (HIV),
hepatitis B, or
hepatitis C, is not used. The risk of contracting a
virus from donated factor concentrate is very low. But people who receive many
units of donated factor concentrate over their lives have a slightly increased
risk of being infected with one of these viruses. In addition,
hepatitis A virus and parvovirus (the virus that
causes
fifth disease) are harder to detect and can sometimes
be transmitted through donated factor concentrates.
Clotting factor concentrates are not always effective, because
the body can develop antibodies called
inhibitors, which destroy the newly introduced factor
VIII or IX.
What are the main types of clotting factor replacement?
Clotting factor replacement therapy is a way to
introduce missing or inadequate amounts of clotting factor VIII or IX
components into your blood. Replacing factor VIII will help blood to clot in
people who have hemophilia A. Replacing factor IX will help blood to clot in
people who have hemophilia B. Clotting factor replacement therapy can be used
two ways: on a regularly scheduled basis, to prevent bleeding episodes; or on
demand, to prevent or control a bleeding episode that has occurred or is likely
to occur.
Clotting factor replacement therapy comes in three main forms:
fresh frozen plasma, cryoprecipitate, or factor concentrates.
- Fresh frozen plasma is the
liquid part of blood (plasma) taken from a donor and frozen
for later use.
- Fresh frozen plasma contains all types of clotting
factors, so it can be used to treat a variety of bleeding problems. It is less
expensive than factor concentrates.
- A large amount of plasma is
required to provide enough clotting factor to prevent bleeding. It must be
frozen, so it is usually used in a hospital and is not easily kept at
home.
- Cryoprecipitate is a blood product
that contains all clotting factors, so it can be used to treat many varieties
of bleeding disorders.
- A bleeding episode requires less cryoprecipitate
than fresh frozen plasma because cryoprecipitate has been concentrated.
Cryoprecipitate is not likely to transmit a disease because it is from only one
donor. It is less expensive than donated and recombinant factor
concentrates.
- Although cryoprecipitate is concentrated, a
relatively large amount is still required (compared to factor concentrates and
recombinant products) to increase clotting factors to a safe level.
Cryoprecipitate must be frozen, so it is usually used in a hospital and is not
easily kept at home.
- Factor concentrates are used to
prevent or treat bleeding episodes that occur outside a hospital.
- A factor concentrate that is infused on a
regular basis can prevent some bleeding episodes from occurring. If you have a
factor concentrate infusion soon after a bleeding episode begins, it can
prevent bleeding from becoming severe.
- Clotting factor concentrates
are portable, are easily stored, and can be infused at home.
- Donated factor concentrate is derived from screened blood from
many donors and has a high concentration of factor VIII or IX. Donors are
carefully screened, and donated blood goes through purifying processes that
kill most viruses.
- Recombinant clotting factors are produced in a lab
(using recombinant
DNA technology) and are not derived from donated
blood. Clotting factors for hemophilia A contain some human or animal proteins,
so there is still some risk that they may contain a virus. But the clotting
factors produced for hemophilia B do not contain any human or animal products.
Recombinant clotting factors are much more expensive than clotting factors made
from donated blood.
What are the benefits of regularly scheduled therapy?
You likely will have fewer bleeding episodes, which may be
especially important if you have severe hemophilia. You also will have a lower
risk of serious complications and long-term damage from repeated bleeding
episodes into your muscles or joints.
You may have an improved quality of life. You could more freely
participate in activities and exercises that might otherwise cause a bleeding
injury.
What are the benefits of on-demand therapy?
On-demand therapy is not needed as often as regularly scheduled
treatment, so it is less expensive. Insurance companies are more likely to pay
some of the cost.
You will not have to give yourself injections as often.
If a bleeding episode is suspected, prompt on-demand infusions
can quickly and effectively control bleeding. You will likely get familiar with
your body and be able to tell when a bleeding episode has started, even before
you have many symptoms.
Infusions can be given before activities where there is a high
risk of bleeding.
What are the risks of regularly scheduled therapy?
Treatment is expensive, especially when clotting factors that are
produced in a lab are used. Insurance companies do not always cover the cost of
regularly scheduled preventive treatment.
If you use donated clotting factors, you increase your risk of
contracting a viral infection.
Usually the infusions must be scheduled 3 times a week, which can
disrupt your daily activities. In addition, some people may have a difficult
time with the frequent injections.
If you use recombinant clotting factors that are produced in a
lab, supplies may not always be available. Shortages are more likely to occur
with recombinant clotting factors than with plasma-derived products.
You may increase your risk of developing an inhibitor.
What are the risks of on-demand therapy?
When bleeding is suspected, a quick response may not always be
practical or feasible.
If you have severe hemophilia with frequent bleeding episodes,
you may not prevent some episodes. As a result, you may develop complications
and long-term damage. Also, some children with severe hemophilia who have
frequent bleeding episodes miss more school than average, which may cause them
to score lower on achievement tests than children who experience fewer bleeding
episodes.2
If you have an unexpected accident, it may be difficult to treat
a bleeding episode.
Serious bleeding, such as after a head injury, poses a great
danger. Head injuries can cause bleeding that may be fatal if they are not
treated immediately.
If you need more information, see the topic
Hemophilia.
