Haemophilia A — MFDS Part 1 MCQ
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Correct answer: B — Factor VIII
Haemophilia A is caused by deficient or dysfunctional factor VIII activity, so B is correct. It is usually an inherited X-linked bleeding disorder. Factor IX deficiency causes haemophilia B, also called Christmas disease. Factor XI and factor VII deficiencies are separate, rarer coagulation disorders and do not cause haemophilia A. Deficiency or dysfunction of von Willebrand factor causes von Willebrand disease. Although von Willebrand factor binds and stabilises circulating factor VIII, it is not the clotting-factor deficiency that defines haemophilia A. This distinction is clinically relevant when assessing patients with an inherited bleeding history before invasive dental treatment.
Reference: Oxford Haemophilia and Thrombosis Centre. Welcome to the Adult Haemophilia Comprehensive Care Centre, section listing bleeding disorders. Oxford University Hospitals NHS Foundation Trust; April 2022, reviewed April 2025. https://www.ouh.nhs.uk/patient-guide/leaflets/files/78305Phaemophilia.pdf