PA20.1-2 | Coagulation Factor Disorders — Haemophilia & vWD — Summary & Reflection

REFLECT

A 35-year-old woman with no prior bleeding history develops sudden-onset haemarthrosis and soft-tissue haematomas. Her aPTT is markedly prolonged, PT is normal, and platelet count is normal. A mixing study does NOT correct, even after immediate mixing.

Consider:
1. What does non-correction on the mixing study indicate? How does this differ from haemophilia A?
2. What is 'acquired haemophilia A' — who gets it and why?
3. How would the approach to this patient differ from a child with congenital Haemophilia A?

Take 3 minutes to write your reasoning before reading the summary block.

KEY TAKEAWAYS

Coagulation Factor Bleeding Disorders — Key Take-Aways

1. Deep-tissue bleeding (haemarthrosis, muscle haematomas, delayed rebleeding) signals secondary haemostasis failure; petechiae and mucocutaneous bleeding signal primary failure.

1. Haemophilia A (factor VIII deficiency, X-linked recessive): isolated prolonged aPTT, normal PT, normal platelets and BT. Severity by factor level. Haemarthrosis → arthropathy. Treatment: factor VIII concentrate; DDAVP in mild disease.

1. Haemophilia B (factor IX, Christmas disease): clinically identical to Haemophilia A; differentiated only by specific factor assays.

1. Von Willebrand disease (commonest inherited bleeding disorder): vWF deficiency impairs both platelet adhesion AND factor VIII stabilisation → dual mucocutaneous + sometimes deep bleeding. Prolonged BT/PFA and variable aPTT. Diagnosed by ristocetin cofactor assay. Treat Type 1 with DDAVP; Types 2/3 with vWF concentrate.

1. PT/aPTT pattern: Intrinsic-only = haemophilias; extrinsic-only = early vitamin K deficiency / factor VII defect; both prolonged = common pathway, liver disease, severe vitamin K deficiency, warfarin.

1. Mixing study: Correction = factor deficiency; non-correction = inhibitor. Time-dependent non-correction = warm-reacting inhibitor (factor VIII autoantibody).

1. Liver disease spares factor VIII (endothelial origin); vitamin K deficiency spares factor V (no gamma-carboxylation needed). Factor V level is the discriminating test.

1. Acquired haemophilia A (autoantibody to factor VIII) presents like Haemophilia A but in adults with no family history — always do a mixing study.