Factor I deficiency

From Dog

Factor I deficiency (congenital afibrinogenemia) is an autosomal-recessive genetic form of hemophilia.

This disease may manifest as a complete lack of fibrinogen (afibrinogenemia), reduced fibrinogen (hypofibrinogenemia) or abnormal fibrinogen (dysfibrinogenemia). Some cases can be caused by antibody production against fibrin components.

These defects produce a mild to severe or fatal bleeding diathesis[1].

Factor I deficiency has been reported in the Chihuahua[2], Bichon Frise[3], St. Bernard, Borzoi, Vizsla and American Collie.

Clinically affected dogs are often asymptomatic until severe trauma or surgical procedures are performed, which can trigger a massive hemorrhagic episode that can be fatal.

Diagnosis is by coagulation screening tests which usually show prolonged prothrombin time (PT), activated partial thromboplastin time and thrombin clotting time. Fibrinogen assays show either no or only trace amounts of fibrinogen.

A differential diagnosis would include other causes of hemophilia, DIC and hepatitis.

Treatment usually requires aggressive plasma cryoprecipitate or whole blood transfusions (15 - 30 mL/kg) until clotting times normalize.


  1. Dodds WJ (1992) Bleeding disorders. In: Handbook of Small Animal Practice, RV Morgan, ed., 2nd Ed. pp:765-777. Churchill Livingstone, New York, New York
  2. Chambers G et al (2013) Treatment of afibrinogenemia in a chihuahua. J Am Anim Hosp Assoc 49(1):70-74
  3. Wilkerson MJ et al (2005) Afibrinogenemia and a circulating antibody against fibrinogen in a Bichon Frise dog. Vet Clin Pathol 34(2):148-155