Micro & Immunology · patient case question
Von Willebrand factor is functionally associated with which coagulation factor?
Patient case: The Hypothyroid Patient with an Aching Jaw
Patient: 54-year-old female
Chief Complaint: Generalized aching in the jaws and fatigue.
Background: Hashimoto thyroiditis diagnosed two years ago. Recently also investigated for bone pain; laboratory work shows a raised alkaline phosphatase with low vitamin D.
Medications: Levothyroxine
Vital Signs: BP 118/74 mmHg · HR 58 bpm · RR 14 · T 97.4°F
Findings: Dry cool skin, coarse hair, periorbital puffiness, slow relaxation of deep tendon reflexes. Intraorally the tongue is enlarged with scalloped margins. Panoramic film shows generalized reduced bone density.
Show answer and explanation
Correct answer: B. Factor VIII
- A. Factor VII is the extrinsic pathway factor measured by the PT and INR. It has no relationship to vWF.
- B. CORRECT. FACTOR VIII. Von Willebrand factor has two distinct jobs: it mediates PLATELET ADHESION to exposed subendothelial collagen at the site of injury, and it acts as the CARRIER PROTEIN that stabilises factor VIII in the circulation. Without vWF, factor VIII is degraded rapidly and its level falls — which is why von Willebrand disease produces a combined defect of primary haemostasis (prolonged bleeding time, abnormal platelet function) and a secondary reduction in factor VIII activity with a prolonged aPTT.
- C. Factor IX deficiency is haemophilia B (Christmas disease). It is unrelated to vWF.
- D. Factor XIII cross-links fibrin to stabilise the clot; its deficiency causes delayed bleeding with a normal PT and aPTT.
Note: Von Willebrand disease is the COMMONEST inherited bleeding disorder, usually autosomal dominant. Dental management: DESMOPRESSIN (DDAVP) releases stored vWF and factor VIII from endothelium and is effective in Type 1, the commonest form. Add tranexamic acid, local haemostatic measures, and avoid aspirin and NSAIDs.
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