Hemophilia B (Variant 2)

Hemophilia B is a clotting disorder characterized by a deficiency of factor IX, which is essential for the formation of blood clots. This condition results in hemostatic problems that can trigger severe bleeding. The genetic variant responsible is located in the F9 gene, responsible for encoding coagulation factor IX.

Symptoms

Hemophilia B in cats presents with various symptoms such as intermittent loss of appetite, fatigue, fever and difficulty walking. These signs may appear in different combinations. Severely affected individuals may die at birth as a result of umbilical hemorrhage, while those who survive the neonatal period may suffer from clotting problems such as hemorrhage and hematoma formation.

Disease Management

Treatment of hemophilia B focuses primarily on managing and preventing bleeding episodes caused by clotting factor IX deficiency. Options include transfusions of Fresh Frozen Plasma (FFP) and hemostatic medications to control active bleeding.

Genetic basis

This disease follows an X-linked recessive mode of inheritance. Recessive X-linked inheritance means that females must receive two copies of the mutation or pathogenic variant (one from each parent) to develop the disease, whereas males need only one copy of the mutated gene or variant from the mother to develop the disease. Male cats usually show symptoms of the disease. Each male kitten born to a mother carrying the mutation has a 50% chance of inheriting the mutation and thus the risk of developing the disease. Females that do not carry the mutation are not at increased risk of having affected kittens. Breeding between cats carrying genetic variants that can cause disease is not recommended, even if they do not show symptoms.

Technical report

Hemophilia B, also known as Christmas disease, is an X-linked inherited clotting disorder manifested by a deficiency of functional clotting factor IX. This factor is crucial in the blood clotting cascade, facilitating the formation of clots to stop bleeding. In the F9 gene, responsible for the production of coagulation factor IX, two genetic variants associated with hemophilia B have been identified in domestic cats. In this case, we analyzed the single nucleotide change (c.1150C>T) in exon 8, which encodes an important part of the catalytic domain of the protein. This specific change leads to the formation of a premature stop codon, resulting in the production of a truncated protein.

Most affected breeds

Domestic

Bibliography

Goree M, Catalfamo JL, Aber S, et al. Characterization of the mutations causing hemophilia B in 2 domestic cats. J Vet Intern Med. 2005 Mar-Apr.