Congenital Bleeding Disorders

Both clinical and basic problems related to the congenital bleeding disorders continue to confront hematologists. On the forefront are efforts to bring genetic correction of the more common bleeding disorders such as hemophilia A to the clinic in a safe and accessible manner. A second issue, particularly for patients with hemophilia, is the development of inhibitors—questions of how they arise and how to prevent and treat these problems that confound otherwise very successful replacement therapy and allow patients to maintain normal lifestyles. A third issue is the continuing question of diagnosis and management of von Willebrand disease, the most common congenital bleeding disorder, especially in individuals who have borderline laboratory values, but have a history of clinical bleeding. In Section I, Dr. Christopher Walsh discusses general principles of effective gene transfer for the hemophilias, specific information about viral vectors and non-viral gene transfer, and alternative target tissues for factor VIII and factor IX production. He highlights information about the immune response to gene transfer and reviews data from the hemophilia gene transfer trials to date. The future prospects for newer methods of therapy such as RNA repair and the use of gene-modified circulating endothelial progenitors are presented as possible alternatives to the more traditional gene therapy approaches. In Section II, Dr. Nigel Key focuses on inhibitor development in patients with hemophilia A. He reviews the progress in our understanding of the risk factors and presents newer information about the immunobiology of inhibitor development. He discusses the natural history of these inhibitors and the screening, laboratory diagnosis, and treatment, including the use of different modalities for the treatment of acute bleeding episodes. Dr. Key also presents information about the eradication of inhibitors by immune tolerance induction and reviews recent information from the international registries regarding the status and success of immune tolerance induction. In Section III, Dr. Margaret Rick discusses the diagnosis, classification, and management of von Willebrand disease. Attention is given to the difficulty of diagnosis in patients with mild bleeding histories and borderline laboratory test results for von Willebrand factor. She presents the value of different laboratory assays for both diagnosis and classification, and she relates the classification of von Willebrand disease to the choice of treatment and to the known genetic mutations. Practical issues of diagnosis and treatment, including clinical cases, will be presented.