Hemophilia B (Cairn terrier type) is an inherited bleeding disorder affecting Cairn terriers. Hemophilia B (Cairn terrier type) is caused by a deficiency of coagulation factor IX, an essential protein needed for normal blood clotting. While there is some variation in bleeding tendency with this disease, Cairn terriers generally exhibit more severe clinical signs. Affected dogs bruise easily and often get blood filled masses (hematomas) under their skin and within muscles with mild trauma. They can also have internal bleeding and bloody or dark tarry feces. Dogs may show signs of lameness or stiffness if bleeding in the joints is present. A mildly affected dog may present with easy and excessive bruising and frequent nosebleeds. There is significant risk for prolonged bleeding after surgery or trauma, and in some cases, the bleeding may be severe enough to cause death. Veterinarians performing surgery on known affected dogs should have ready access to blood banked for transfusions. Most dogs will have a normal lifespan with this condition despite increased blood clotting times.