Hemophilia B / factor IX deficiency (F9-related) - Cairn Terrier

What does this test examine?

This genetic test analyses the F9 variant c.1253G>A for Hemophilia B in the Cairn Terrier. The condition is also known as factor IX deficiency, Christmas disease, Christmas factor deficiency and F9-related bleeding disorder.

What does this disease mean?

Hemophilia B is an inherited blood-clotting disorder in which factor IX activity is absent or strongly reduced. Affected dogs can bleed for prolonged periods or spontaneously, develop bleeding into joints, muscles, chest or abdomen, and have serious post-bleeding after injury, tooth eruption, injection or surgery.

F9 encodes coagulation factor IX, an essential component of the intrinsic clotting pathway. Variants that reduce the amount or function of factor IX disrupt stable clot formation. As a result, even minor tissue damage can lead to unusually prolonged or life-threatening bleeding.

X-linked inheritance and result

Hemophilia B follows an X-linked recessive inheritance pattern. Males have one X chromosome; when the tested variant is present on that chromosome, it causes the disease. Females with one copy are usually carriers and can pass the variant on; females with two copies are expected to be genetically affected.

• Clear: the tested variant was not detected.
• Carrier: one copy was detected; this usually indicates a carrier female.
• Affected: the variant is present hemizygously in a male or in two copies in a female; this causes Hemophilia B.

Practical value of this test

This test helps breeders and owners identify a serious bleeding risk early and accurately. For X-linked diseases, carrier knowledge is especially important because healthy females can silently pass the variant to sons that become affected.

• Supports breeding selection and safe mating plans.
• Helps identify carrier females before the variant is passed on silently.
• Provides clear genetic information before procedures, mating or sale of breeding animals.
• Helps manage risk lines and reduce the number of affected males.