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Hemophilia
in
Canis familiaris
(dogs)
General information
MIM number: 306900
MIA number: 000438
What is hemophilia?
Hemophilia is a bleeding disorder of
varying severity that is due to a deficiency
in specific clotting factors.
It is an X-linked, recessive disorder which
is one of the few sex-linked traits in dogs.
Hemophilia found in dogs are very closely
related to the hemophilia found in
humans.
Sex
chromosomes
Chromosomes present in a
female dog
There are two major types of hemophilia:
Hemophilia A is defective in coagulation factor
VIII and is sometimes called royal hemophilia
because it occurred in descendants of Queen
Victoria.
Hemophilia B is defective in coagulation factor
IX and is also known as Christmas disease
because it was first observed in a patient
named Stephen Christmas.
Both hemophilia types are X-linked
disorders but however differentiated
because it occurs on different genes on
the X chromosome.
History
Queen Victoria
Molecular Genetics of hemophilia
The molecular basis of hemophilia B are
mutations in the F9 gene.
This genetic disorder is caused by many
different types of mutations such as:
Deletions
Insertions
Point mutations
Duplications
Inversions
Because males have only 1 X
chromosome, a male dog is either affected
or clear of the defect.
Females, with 2 X chromosomes, may be
affected (abnormal gene on both
chromosomes), clear, or a carrier with no
clinical signs (one gene affected).
In effect, the disease is carried by
females but affects mostly males.
Factor IX
F9 gene
Cytogenetic Location: Xq27.1q27.2
The factor IX gene is about
34kb long.
Encompasses 8 exons and 7
introns.
Encodes a protein that
consists of 415 amino acids
And has a molecular weight of
57 000D
How does hemophilia work?
Clotting Cascade
Factor XII
Types of dogs affected
Bull Terrier
Lhasa Apso
Airedale Terrier
Labrador
Clinical signs of hemophilia B
Symptoms vary widely, based on the
severity of the bleeding disorder
bloody diarrhea
bleeding under the skin
lameness
Clinical signs of hemophilia B
Where hemophilia is more severe, you may
see signs of a problem at a fairly early age
Pups may have prolonged bleeding associated
with the loss of baby teeth.
Bleeding under the skin
Bleeding into muscles or joints will often cause
lameness.
Unfortunately, dogs with severe hemophilia
often die or are euthanized because of recurrent
or uncontrollable bleeding problems.
Detection of hemophilia
Diagnosis is made through blood tests to
determine:
Blood clotting
Level of clotting factors
Missing clotting factors
How is hemophilia treated?
There is no cure for this disorder.
Periodic transfusions
Administer fresh plasma, fresh frozen
plasma, or cryosupernatant (factor IX)
plasma.
Gene Therapy