Quebec platelet disorder

Quebec platelet disorder (QPD), also known as factor V Quebec, is a rare inherited bleeding disorder first described in families from the province of Quebec, Canada. It is characterized by a unique defect in platelet alpha-granule proteins, where there is increased amounts of urokinase plasminogen activator (uPA) within platelets. This overexpression of uPA leads to degradation of alpha-granule proteins, including factor V, fibrinogen, thrombospondin, osteonectin, and von Willebrand factor stored within the platelets. As a result, patients experience delayed-onset bleeding after trauma or surgical procedures, rather than the immediate bleeding seen in many other platelet disorders. The primary body system affected is the hematologic system. Key clinical features include delayed-onset bleeding (typically 12–24 hours after a hemostatic challenge), mucocutaneous bleeding, joint bleeding (hemarthrosis in some cases), and a variable bleeding tendency that can range from mild to severe. Platelet counts are usually normal, and standard platelet aggregation studies may appear normal or near-normal, which can make diagnosis challenging. The disorder is caused by a tandem duplication of the PLAU gene (encoding urokinase plasminogen activator) on chromosome 10. Treatment of Quebec platelet disorder differs from typical platelet disorders. Platelet transfusions are generally ineffective because the underlying problem is excessive fibrinolysis within the platelet. Instead, fibrinolytic inhibitors such as tranexamic acid or epsilon-aminocaproic acid are the mainstay of treatment and are effective in controlling and preventing bleeding episodes. These antifibrinolytic agents should be administered prophylactically before surgical or dental procedures. Awareness of this condition is important because misdiagnosis can lead to inappropriate treatment with platelet transfusions that fail to control bleeding.

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