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Clinical outcome after diagnosis of hemophilia A in dogs

Aslanian, M.E., Sharp, C.R.ORCID: 0000-0002-1797-9783, Rozanski, E.A., de Laforcade, A.M., Rishniw, M. and Brooks, M.B. (2014) Clinical outcome after diagnosis of hemophilia A in dogs. Journal of the American Veterinary Medical Association, 245 (6). pp. 677-683.

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Objective — To evaluate the clinical course of dogs with hemophilia A (factor VIII deficiency) and to determine whether factor VIII coagulant activity (FVIII:C) was associated with severity of clinical signs and outcome.

Design — Survey study.

Sample — Respondent information for 39 client-owned dogs with FVIII deficiency.

Procedures — Information was obtained via a survey distributed to the American College of Veterinary Internal Medicine and American College of Veterinary Emergency and Critical Care email list serves and to the Veterinary Information Network community to identify dogs with hemophilia A (FVIII:C ≤ 20%). Severity of FVIII deficiency was classified as mild (FVIII:C, 6% to 20%), moderate (FVIII:C, 2% to 5%), or severe (FVIII:C, < 2%).

Results — Data for 39 dogs (38 males and 1 female) were compiled. Mixed-breed dogs, German Shepherd Dogs, and Labrador Retrievers were most commonly affected. In most (34/39) dogs, disease was diagnosed at < 1 year of age. Bleeding associated with teething, minor trauma, vaccination, and elective surgical procedures most commonly prompted FVIII:C testing. Affected dogs had similar signs of spontaneous hemorrhage regardless of the magnitude of FVIII deficiency. Four dogs were euthanized without treatment at the time of diagnosis. Thirty dogs received ≥ 1 blood transfusion; FVIII:C did not appear to influence transfusion requirements.

Conclusions and Clinical Relevance — Results indicated that dogs with hemophilia A have variations in clinical course of the disease and may have a good long-term prognosis. Residual FVIII:C may not be useful for predicting severity of clinical signs, transfusion needs, or long-term prognosis.

Hemophilia A is an X-linked recessive bleeding disorder caused by deficiency or dysfunction of FVIII. Although classically inherited in an X-linked familial pattern in both humans and dogs, de novo mutations of the FVIII gene located on the long arm of the X chromosome may also occur, which results in sporadic cases in previously unaffected families.1,2

Clinical severity of hemophilia A in humans, as defined by frequency of bleeding events and transfusion needs, is inversely related to residual FVIII:C,3 but to our knowledge, no such population studies have been reported for dogs. Factor VIII deficiency in humans is classified as mild (FVIII:C, 6% to 20%), moderate (FVIII:C, 2% to 5%), or severe (FVIII:C, < 2%).2–4 Severely affected humans have frequent episodes of spontaneous hemorrhage that require periodic FVIII replacement therapy, which is most often administered as FVIII concentrates and rarely as transfusions of cryoprecipitate, FFP, or fresh whole blood. Recipients of multiple transfusions may develop anti-FVIII antibodies that bind to transfused FVIII, thereby inhibiting coagulant activity; this has been verified in both humans and dogs.5–8

Hemophilia A in dogs is most commonly suspected because of episodes of clinical hemorrhage and is confirmed by identification of a specific deficiency of FVIII:C in the absence of deficiencies of other coagulation factors. Clinical signs in dogs with hemophilia A include subcutaneous hematoma and intermittent bleeding at an injection site, prolonged bleeding at eruption sites of deciduous teeth, hematoma formation or prolonged bleeding after surgery, abnormal bleeding from minor wounds, and lameness attributable to hemarthrosis.9 Although dogs with hepatic synthetic failure and consumptive and dilutional coagulopathies may have markedly low FVIII:C, these patients typically have obvious underlying disease and combined deficiencies of coagulation factors and fibrinogen that differentiate them from dogs with hemophilia A.

The long-term management and survival rate of dogs with hemophilia A maintained in a research colony have been described6; however, to the authors’ knowledge, no comparable information is available regarding client-owned pet dogs. The objectives of the study reported here were to describe the long-term outcome for a group of dogs with hemophilia A at clinical practices and to determine the relationship between FVIII:C at diagnosis and severity of clinical signs and prognosis.

Item Type: Journal Article
Publisher: American Veterinary Medical Association
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