Hemophilia A in two related quarter horse colts.

The paper discusses two related Quarter Horse colts diagnosed with hemophilia A, a blood clotting issue often causing severe bleeding. The disease was noticeable by symptoms such as dyspnea and dysphagia, eventually leading to the fatality of one colt and confirmed by specific assays.

Clinical Manifestation of Hemophilia A

• The two colts studied presented severe hemorrhagic diathesis, an abnormal susceptibility to bleeding, which is a common characteristic of hemophilia A.
• Different clinical signs were evident in each colt, with one showing signs of dyspnea (difficulty breathing) and dysphagia (difficulty swallowing), both of which were traced back to cranial cervical hematoma – a blood clot in the neck area. This indicates that hemophilia A may cause severe symptoms relating to blood clotting within the horse’s body.
• The second colt suffered from intra-abdominal hemorrhage, a severe internal bleeding in the abdominal region which resulted in its unfortunate death. This signifies the risk of fatal complications caused by this disease.

Diagnosis and Pathogenesis of Hemophilia A

• The disease was diagnosed by confirmed factor VIII:C deficiency, a defect in the intrinsic coagulation pathway which impairs the body’s ability to clot blood effectively. The deficiency was indicated through specific coagulation tests:
• An abnormally prolonged activated partial thromboplastin time (APTT) – a test that measures clotting time.
• Normal prothrombin time indicated that part of the blood clotting process was functioning properly, meaning the problem lay elsewhere.
• Normal primary bleeding time suggested the initial platelet plug formation after blood vessel injury is unaffected.
• The deficiency was further confirmed by assays (testing methods) for Factor VIII:C. These tests scientifically proved the predetermined cause of the disorder.

Inheritance of Hemophilia A

• Finally, the paper establishes that hemophilia A is inherited as an X chromosome-linked trait. This means it is often passed from mothers to their sons, as males have one X chromosome that can become defective causing this disease.
• It is suggested that because the two colts studied were related, they likely inherited this disorder from a common maternal lineage.