Quebec platelet disorder

Individuals with QPD are at risk for experiencing a number of bleeding symptoms, including joint bleeds, hematuria, and large bruising.[4]

The disorder is characterized by large amounts of uPA in platelets.[3] Consequently, stored platelet plasminogen is converted to plasmin, which is thought to play a role in degrading a number of proteins stored in platelet α-granules.[5] These proteins include platelet factor V, von Willebrand factor, fibrinogen, thrombospondin-1, and osteonectin.[3] There is also a quantitative deficiency in the platelet protein multimerin 1 (MMRN1). Furthermore, upon QPD platelet activation, uPA can be released into forming clots and accelerate clot lysis, resulting in delayed-onset bleeding (12-24hrs after injury).[6]

In 2010, the genetic cause of QPD was determined as a mutation involving an extra copy of the gene encoding uPA.[7] The mutation causes overproduction of uPA, an enzyme that accelerates blood clot breakdown.[2]

Genetic testing is the only way to definitively diagnose QPD, as most other tests cannot confirm this diagnosis.[8] Methods include polymerase chain reaction or Southern blotting for the genetic sequence, or assays for platelet uPA levels or platelet granules.[8]

Bleeding episodes are treated using antifibrinolytic medication, particularly tranexamic acid, to prevent fibrinolysis.[8]

The discovery was made by a team of doctors at McMaster University led by Dr. Catherine Hayward, a hematologist.[9]