MBBS viva · Haematology
Coagulation disorders (haemophilia and von Willebrand disease) — viva
A final-prof viva on the inherited coagulation disorders — distinguishing haemophilia A/B from von Willebrand disease at the bedside and the bench, interpreting the coagulation screen, and justifying factor replacement, DDAVP and emicizumab at dose-level detail.
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NEET-PGINICETUSMLEPLAB
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Interpretation
The examiner opens with: "A 4-year-old boy has recurrent swollen painful knees and a maternal uncle who bled to death as a child. His APTT is prolonged; PT and platelets are normal. Talk me through the diagnosis and your management."
- The pattern — male child, X-linked family history, deep-tissue bleeds (haemarthrosis), isolated prolonged APTT that corrects on mixing — is haemophilia (factor VIII deficiency in ~80 percent, factor IX in ~20 percent).[1]
- Confirm with factor VIII and IX assays; grade severity by the factor level (severe under 1 percent, moderate 1 to 5 percent, mild over 5 percent).
Key points
The examiner will probe each; defend at viva depth:
- Haemophilia vs VWD — haemophilia is X-linked (males) with deep bleeds (joints, muscles); VWD is autosomal dominant, the commonest inherited bleeding disorder, with mucocutaneous bleeding (epistaxis, menorrhagia, gums). VWD is a double hit: defective platelet adhesion AND a secondary factor VIII deficiency because vWF is its carrier.[2]
- The coagulation screen and mixing study — isolated APTT prolonged, PT and platelets normal; a mixing study that corrects = factor deficiency, one that does not correct = inhibitor (acquired haemophilia, lupus anticoagulant).[1]
- Acute bleed management — factor replacement FIRST, do not wait for levels or imaging. Raise VIII/IX to 50 to 80 percent for a joint or muscle bleed, to 100 percent for ICH or surgery. DDAVP (desmopressin) releases stored VIII and vWF — works for mild haemophilia A and type 1 VWD, useless in severe disease.[1]
- Prophylaxis — emicizumab (subcutaneous bispecific antibody bridging IXa and X, mimicking VIIIa) is now first-line for severe haemophilia A, with or without inhibitors; extended half-life factor IX for haemophilia B.[1]
- Inhibitors — neutralising antibodies to VIII/IX in 10 to 30 percent of severe haemophilia A; treat bleeds with bypassing agents (recombinant factor VIIa or FEIBA); prophylaxis with emicizumab.
- Gene therapy — valoctocogene roxaparvovec (haemophilia A) and etranacogene dezaparvovec (haemophilia B): single IV infusions giving durable factor expression — a potential functional cure.
- Avoid — intramuscular injections, NSAIDs, antiplatelets; avoid epidural anaesthesia in VWD unless vWF activity is over 50 IU/dL on the day.[2]
References
- Berntorp E, et al. Haemophilia. Nature Reviews Disease Primers 2021.[1]
- Connell NT, et al. ASH-ISTH-NHF-WFH 2021 guidelines on VWD. Blood Advances 2021.[2]
References2ShowHide
- [1]Berntorp E, Fischer K, Hart DP, et al. Haemophilia. Nature Reviews Disease Primers, 2021.PMID 34168126
- [2]Connell NT, Flood VH, Brignardello-Petersen R, et al. ASH ISTH NHF WFH 2021 guidelines on the management of von Willebrand disease. Blood Advances, 2021.PMID 33570647