Hemophilia A
Alternative names
Classical hemophilia;
Factor VIII deficiency hemophilia
Definition
Hemophilia A is a hereditary
blood coagulation disorder caused by a deficient
activity of plasma protein factor VIII, which
affects the clotting property of blood.
Causes
and risks
Hemophilia is a group
of hereditary bleeding disorders of specific
blood clotting factors classified as hemophilia
A and B. Hemophilia A is the most common of
these disorders and is the result of a deficiency
of clotting factor VIII.
The disorder is caused
by an inherited sex-linked recessive trait with
the defective gene located on the X chromosome.
Females carry two copies of the X chromosome,
and therefore if the factor VIII gene on one
chromosome is defective, the gene on the other
chromosome can compensate. Males, however,
carry only one X chromosome, so if the factor
VIII gene on that chromosome is defective, they
will have the disease.
Females with one defective
factor VIII gene are carriers of this trait.
Fifty percent of the male offspring of female
carriers have the disease and 50% of their female
offspring are carriers. All female children
of a male hemophiliac are carriers of the trait.
The severity of symptoms can vary with this
disease, and the severe forms become apparent
early on. Bleeding is the hallmark of the disease
and sometimes, though not always, occurs if
an infant is circumcised. Additional bleeding
manifestations make their appearance when the
infant becomes mobile.
Mild cases may go unnoticed
until later in life when they occur in response
to surgery or trauma. Internal bleeding may
happen anywhere, and bleeding into joints is
common. Risk factors are a family history of
bleeding and being male.
The incidence of hemophilia
A is 1 out of 5,000 men.
Prevention
- Genetic counseling
- Prenatal intrauterine
diagnosis with termination of pregnancy as
an option
Symptoms
- Bruising
- Spontaneous bleeding
- Bleeding into joints
and associated pain and swelling
- Gastrointestinal
tract and urinary tract hemorrhage
- Blood in the urine
or stool
- Prolonged bleeding
from cuts, tooth extraction, and surgery
Signs
and tests
Coagulation studies involving many tests are performed
if the person tested is the first one in the family
to have a bleeding disorder. Once the defect has
been identified, other family members will need
less testing to diagnose the disorder.
- Prolonged PTT
- Normal prothrombin
time
- Normal bleeding time
- Normal fibrinogen
level
- Low serum factor
VIII activity
Treatment
Standard treatment is
infusion of factor VIII concentrates to replace
the defective clotting factor. The amount infused
depends upon the severity of bleeding, the site
of the bleeding, and the size of the patient.
Mild hemophilia may be treated with infusion
of cryoprecipitate or desmopressin (DDAVP),
which causes release of factor VIII that is
stored within the body on the lining of blood
vessels.
To prevent a bleeding crisis, people with hemophilia
and their families can be taught to administer
factor VIII concentrates at home at the first
signs of bleeding. People with severe forms
of the disease may need regular prophylactic
infusions.
Depending on the severity of the disease, DDAVP
or factor VIII concentrate may be given prior
to dental extractions and surgery to prevent
bleeding.
Immunization with Hepatitis B vaccine is necessary
because of the increased risk of exposure to
hepatitis due to frequent infusions of blood
products.
Patients
who develop an inhibitor to factor VIII may
require treatment with other clotting factors
such as factor VIIa, which can aide clotting
even in the absence of factor VIII.
Support
groups
The stress of illness can
often be helped by joining a support group where
members share common experiences and problems.
See hemophilia - support group.
Prognosis
With treatment, the outcome
is good. Most people with hemophilia are able
to lead relatively normal lives. A small percentage
of people with hemophilia will develop inhibitors
of factor VIII, and may die from loss of blood. 
