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CHS Research Grants for 2005

Fibrinolytic Variables in Severe Hemophilic A Patients

1st year funding
Dr. Jerome Teitel
St. Michael’s Hospital

The bleeding tendency of people with severe hemophilia varies considerably. This can be explained by differences in levels of their deficient proteins (clotting factor VIII or IX) which are too small to be easily measurable. We think that an additional source of variability could lie in fibrinolysis, the process by which blood clots dissolve. Severe hemophilia patients who have rapid fibrinolysis (clots that dissolve quickly) might tend to bleed more severely than others. In this project, we propose to conduct a thorough and systematic study to test the hypothesis that the bleeding tendency in severe hemophilia is correlated with increased fibrinolytic activity. We will measure the levels of four key blood proteins which contribute to fibrinolysis in 100 severe hemophilia patients. We will also monitor the number of bleeding episodes as well as the amount of factor VIII or IX concentrate that these patients have needed over the preceding 2 years. We will statistically determine whether increased values of the fibrinolytic proteins correlate with increased bleeding tendency, and vice versa. At the end of this project, we hope to better our understanding of why bleeding tendencies in severe hemophilia patients are variable. If our hypothesis is confirmed, we will be able to provide a novel rationale for individualized management approaches. These may include selecting target amount of factor VIII or IX for treatment or prevention of bleeding in hemophilia patients. It may also include selecting patients for prophylaxis with clotting factor concurrently with factor VIII or IX replacement therapy, after surgery and other interventions. We may also be able to predict the risk of clotting of central venous catheters, a serious complication of propylactic factor VIII or IX treatment in young children.

Genetic Differences Between Obligate Carriers of Type 3 VWD and Individuals with Type 1 VWD

1st year funding
Dr. Paula James
Queen’s University, Kingston, Ontario
CHS Research Program

Von Willebrand disease (VWD) is the most common known inherited bleeding disorder in humans, affecting as many as 1% of the population. People with VWD have difficulty with bleeding from mucous membranes such as the nose, mouth or lining of the uterus, or can have problems with bleeding after injuries, dental work or surgical procedures. There are 3 subtypes: Type 1 VWD is the most common and least severe and is caused by a mild to moderate deficiency of a blood clotting factor called von Willebrand factor (VWF). Type 3 VWD is the least common and most severe and is caused by a severe deficiency of VWF. Type 2 VWD is caused by VWF that doesn’t function properly.

Type 1 VWD is inherited from one parent while Type 3 VWD is inherited from both parents. In this study, entitled Genetic Differences Between Obligate Carriers of Type 3 VWD and Individuals with Type 1 VWD, we are interested in examining the genetic changes in VWD. A person affected with Type 1 VWD would have inherited it from one parent, while a person affected with Type 3 VWD must have inherited it from both parents. A parent of an individual with Type 3 VWD is usually not affected by any bleeding problem and is referred to as a “carrier”. By using special techniques that allow us to examine an individual’s genetic make-up, we hope to improve our understanding of the types of genetic changes that might lead to Type 1 VWD and those that would lead to being a carrier for Type 3 VWD.