Genetic basis of Haemophilia B (Variant 1) - in cats is an X-linked recessive bleeding disorder caused by mutations in the F9 gene, which encodes coagulation factor IX. In this condition, males, having only one X chromosome, are more commonly affected since a single mutated copy causes the disease. Females require two copies (homozygous) of the mutation to be affected and are usually carriers if heterozygous. Variant 1 refers to a specific mutation in the F9 gene found in domestic cats that results in deficient or nonfunctional factor IX protein. One such mutation involves a premature stop codon in exon 8, disrupting the protein's catalytic domain.
Pathophysiology - Factor IX is a protein essential for blood clotting. In Haemophilia B, mutations in the F9 gene reduce or eliminate factor IX activity, impairing the blood coagulation cascade. This deficiency leads to prolonged bleeding times and failure to properly form blood clots after injury. The disease manifests mainly as abnormal bleeding episodes, especially following trauma or surgery, because the normal clotting process is compromised.
Complications - Affected cats, mostly males, may show: Prolonged bleeding after injuries or surgical procedures. Spontaneous bleeding episodes, including in joints causing lameness and pain. Bruising and swelling under the skin due to internal bleeding. Intermittent lethargy, anorexia, and fever potentially related to bleeding complications. In severe cases, life-threatening hemorrhages.
Why This Matters to Breeders and Vets - Genetic Screening: is vital to identify carriers (mainly females) and affected males to prevent producing affected kittens through breeding. Breeding Decisions: Avoiding mating of a carrier female with an affected or carrier male reduces risk of disease propagation.Veterinary Care: Awareness of Haemophilia B allows prompt diagnosis and appropriate management of bleeding risks in affected cats, including during surgeries or injuries.Male Predominance: Because it is X-linked, most affected cats are male, making pedigree analysis and genetic testing crucial for breed health management.
Summary - Haemophilia B (Variant 1) in cats is an X-linked recessive disorder caused by mutations in the F9 gene coding for coagulation factor IX, leading to impaired blood clotting. It predominantly affects male cats, causing prolonged bleeding, bruising, and hemorrhagic complications. Genetic testing and careful breeding strategies are essential for prevention, while veterinary knowledge supports early diagnosis and effective management to improve cat welfare.
