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Factor V (Quebec): a bleeding diathesis associated with a qualitative platelet Factor V deficiency
The Journal of Clinical Investigation
|October 1, 1984
Summary
Bleeding disorder in a family linked to low platelet Factor V. This essential platelet factor is crucial for stable hemostasis after trauma, impacting clot formation.
Area of Science:
- Hematology
- Molecular Biology
- Genetics
Background:
- Autosomal dominant bleeding disorder identified in a French-Canadian family.
- Characterized by severe bleeding post-trauma, mild thrombocytopenia, and reduced Factor V clotting activity.
Observation:
- Prolonged Stypven times in affected individuals suggested platelet dysfunction in prothrombinase complex assembly.
- Analysis of plasma and platelets revealed normal Factor V antigen levels but critically low functional activity in platelets.
Findings:
- Platelet Factor V functional activity was extremely low (2-4%) relative to antigen levels.
- Plasma Factor V functional activity was moderately reduced (40-65%) compared to antigen levels.
- Prothrombin activation kinetics confirmed normal thrombin-activated platelet function with added Factor Va, ruling out inhibitors or unstable Factor V.
Implications:
- The bleeding diathesis is primarily attributed to deficient platelet Factor V, not plasma Factor V.
- Platelet Factor V is essential for maintaining stable and prolonged hemostasis, particularly after trauma.