Genetic basis of Afibrinogenemia - is caused by a mutation in the FGA gene (fibrinogen alpha chain), leading to the absence or severe deficiency of fibrinogen, a critical protein for blood clotting. Variant 1 is typically described as a 1 base pair deletion (frameshift mutation) in the FGA gene on chromosome 15 (example: chr15:52585180 T deletion in Dachshunds). This mutation results in truncated dysfunctional fibrinogen proteins, disrupting normal clot formation. The condition follows an autosomal recessive inheritance pattern: dogs must inherit two copies of the mutation (one from each parent) to be affected; carriers have one copy and are typically asymptomatic. Though characterized primarily in Dachshunds (including miniature longhaired, smooth, wirehaired, and standard variants), the mutation has been found across multiple Dachshund lines and possibly other breeds through carriers.
Pathophysiology - Deficiency or absence of fibrinogen (clotting factor I) impairs the final step of the coagulation cascade, preventing effective blood clot formation. Affected dogs therefore have severe bleeding tendencies, with blood failing to clot properly after injury or spontaneously. Early signs may be seen from birth, including bleeding from the umbilical cord. Dogs with the condition can develop spontaneous bruising, nosebleeds, gum bleeding, hematomas, internal bleeding, and joint bleeds resulting in lameness.
Complications - Severe and potentially life-threatening bleeding episodes, often triggered by trauma, surgery, or spontaneously. Blood-filled masses (hematomas) under the skin or in muscles. Internal hemorrhages that can cause dark, tarry stools or blood in urine. Joint bleeding can cause pain, lameness, and mobility issues. Despite supportive care, many affected dogs do not survive past one year. Prolonged clotting times are diagnostic (PT, aPTT, TT tests are prolonged).
Why This Matters to Breeders and Vets - Early diagnosis via genetic testing enables better clinical management and avoids high-risk matings. Breeders can prevent affected puppies by identifying carriers and avoiding carrier-to-carrier matings. Veterinarians can advise owners on bleeding risk management and prepare for possible emergencies. Genetic testing is essential to eliminate this severe bleeding disorder from Dachshund breeding lines and minimize its spread.
Summary - Afibrinogenemia, Variant 1, is an autosomal recessive clotting disorder caused by a frameshift mutation in the FGA gene, notably in Dachshunds. It results in a severe deficiency of fibrinogen and life-threatening bleeding problems. Genetic testing allows breeders to identify carriers and avoid producing affected dogs. Veterinary awareness improves diagnosis and care of affected individuals.