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von Willebrand Disease
What is
von Willebrand Disease?
Von
Willebrand Disease is a
bleeding disorder caused
by a defect or
deficiency of a blood
clotting protein, called
von Willebrand Factor.
The disease is estimated
to occur in 1% to 2% of
the population. The
disease was first
described by Erik von
Willebrand, a Finnish
physician who reported a
new type of bleeding
disorder among island
people in Sweden and
Finland.
Von
Willebrand Factor is a
protein critical to the
initial stages of blood
clotting. This
glue-like protein,
produced by the cells
that line the blood
vessel walls, interacts
with blood cells called
platelets to form a plug
which prevents the blood
from flowing at the site
of injury. People with
von Willebrand Disease
are unable to make this
plug because they do not
have enough von
Willebrand Factor or
their factor is
abnormal.
Researchers have
identified many
variations of the
disease, but most fall
into the following
classifications:
• Type
I: This is the most
common and mildest form
of von Willebrand
disease. Levels of von
Willebrand factor are
lower than normal, and
levels of factor VIII
may also be reduced.
• Type II: In these
people, the von
Willebrand factor itself
has an abnormality.
Depending on the
abnormality, they may be
classified as having
Type IIa or Type IIb. In
Type IIa, the level of
von Willebrand factor is
reduced, as is the
ability of platelets to
clump together. In Type
IIb, although the factor
itself is defective, the
ability of platelets to
clump together is
actually increased.
• Type III: This is
severe von Willebrand
disease. These people
may have a total absence
of von Willebrand
factor, and factor VIII
levels are often less
than 10%.
• Pseudo (or
platelet-type) von
Willebrand disease: This
disorder resembles Type
IIb von Willebrand
disease, but the defects
appear to be in the
platelets, rather than
the von Willebrand
factor.
Von
Willebrand Disease is a
genetic disease that can
be inherited from either
parent. It affects
males and females
equally. A man or woman
with VWD has a 50%
chance of passing the
gene on to his or her
child. There are no
racial or ethnic
associations with the
disorder. A family
history of a bleeding
disorder is the primary
risk factor.
VWD
subtype I and II are
usually inherited in
what is known as a
"dominant" pattern. This
means that if even one
parent has the gene and
passes it to a child,
the child will have the
disorder.
VWD
Type III von Willebrand
disease, however, is
usually inherited in a
"recessive" pattern.
This type occurs when
the child inherits the
gene from both parents.
Even if both parents
have mild or
asymptomatic disease,
their children are
likely to be severely
affected.
Diagnosis of von
Willebrand Disease can
be difficult. Blood
tests can be performed
to determine the amount,
structure and function
of von Willebrand
Factor. Since levels
can vary, sometimes
tests may need to be
repeated. A person
suspected of having von
Willebrand Disease
should be referred to a
hematologist who
specializes in the
diagnosis and treatment
of bleeding disorders.
Usually, people with VWD
bruise easily, have
recurrent nosebleeds, or
bleed after tooth
extraction,
tonsillectomy or other
surgery. Recurrent
nosebleeds are also a
hallmark of VWD. Women
can have increased
menstrual bleeding.
For
minor bleeds, treatment
may be unnecessary.
There are a range of
treatment choices that
depend on whether the
VWD is mild or severe.
Stimate® or desmopressin
acetate (DDAVP), a nasal
spray, is the treatment
of choice for mild von
Willebrand disease.
Bleeding is usually
controlled in
individuals with mild
von Willebrand disease
by using this nasal
spray to boost their own
factor VIII and von
Willebrand levels. DDAVP
may be given to increase
the amount of the von
Willebrand factor long
enough for surgery or
dental procedures to be
performed. DDAVP is a
synthetic product that
carries no risk of
infectious disease.
For
excessive bleeding,
infusions of a factor
VIII concentrate rich in
von Willebrand factor,
such as Humate-P®,
Alphanate® or Koate DVI®,
may be required. Humate-P,
manufactured by ZLB-Behring,
is the only FDA-approved
Factor VIII concentrate
for use in von
Willebrand Disease.
If
trauma occurs or surgery
is anticipated,
desmopressin acetate can
be given as a means of
raising the von
Willebrand factor
level.
Aspirin and many of the
drugs used for pain can
aggravate bleeding
because they interfere
with platelet function.
People who have von
Willebrand disease can
take acetaminophen for
pain relief because it
does not inhibit
platelet function.
The
National Hemophilia
Foundation's Medical and
Scientific Advisory
Council (MASAC) issued a
treatment recommendation
for von Willebrand
disease in 1999.
To access this
recommendation,
click here. To
receive a copy of this
recommendation, call
1-800-42HANDI
1-800-42HANDI . |
