Hemophilia in Canis familiaris dogs General information n

Hemophilia in Canis familiaris (dogs)

General information n n MIM number: 306900 MIA number: 000438

What is hemophilia? n n n 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

n 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. Ø 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. Ø n 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 n n The molecular basis of hemophilia B are mutations in the F 9 gene. This genetic disorder is caused by many different types of mutations such as: Deletions Ø Insertions Ø Point mutations Ø Duplications Ø Inversions Ø

n n n 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 F 9 gene n n n Cytogenetic Location: Xq 27. 1 q 27. 2 The factor IX gene is about 34 kb long. Encompasses 8 exons and 7 introns. Encodes a protein that consists of 415 amino acids And has a molecular weight of 57 000 D

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 n bloody diarrhea n bleeding under the skin n lameness

Clinical signs of hemophilia B Where hemophilia is more severe, you may see signs of a problem at a fairly early age n Pups may have prolonged bleeding associated with the loss of baby teeth. n Bleeding under the skin n Bleeding into muscles or joints will often cause lameness. n Unfortunately, dogs with severe hemophilia often die or are euthanized because of recurrent or uncontrollable bleeding problems.

Detection of hemophilia n Diagnosis is made through blood tests to determine: Blood clotting Ø Level of clotting factors Ø Missing clotting factors Ø

How is hemophilia treated? There is no cure for this disorder. n n Periodic transfusions Administer fresh plasma, fresh frozen plasma, or cryosupernatant (factor IX) plasma.

Gene Therapy