Syndrome de Willebrand acquis : étude d’une série de neuf patients et revue de la littérature

[How to interpret and pursue a prolonged quick time or APTT]

The standard hemostasis workup [quick time (QT), and activated partial thrombin time (APTT)] is very commonly prescribed but its interpretation is often difficult for practitioners who are not specialized in hemostasis. Here, we review the principles of the diagnostic approach to these tests. Only a very basic knowledge of the coagulation cascade is necessary to identify which clotting factor tests to prescribe and to interpret the results. Deficiency in several clotting factors suggests liver dysfunction, disseminated intravascular coagulation (DIC) or vitamin K deficiency. If a single factor is deficient, we review the different causes of acquired deficiencies and briefly discuss the characteristics of the different congenital defects, which generally require specialized management. Lupus anticoagulant is a common and generally benign cause of prolonged APTT to be aware of, which is not related to a hemorrhagic risk. A good knowledge of the diagnostic approach to abnormal QT or APTT generally allows the resolution of the most common situations.

[Von Willebrand disease]

Von Willebrand factor is involved in primary hemostasis (adhesion of platelets to subendothelium and platelet aggregation) and acts as the carrier of coagulation factor VIII. Von Willebrand disease, resulting from a quantitative or qualitative defect of this factor, is the most frequent inherited bleeding disorder. It is mainly responsible for symptoms such as mucocutaneous bleeding and excessive bleeding after trauma or invasive procedures, but can also cause gastro-intestinal bleeding or hemarthrosis in the most severe forms of the disease. There are numerous causes of physiological variation of von Willebrand factor plasma levels which can be responsible for diagnostic difficulty or changes in symptoms over time. Diagnosis relies primarily on clinical symptoms but requires the use of several laboratory analyses: von Willebrand factor activity and antigen testing and factor VIII activity. More specialized assays allow classification of the disease in various types and subtypes which imply different management strategies (types 1, 2A, 2B, 2M, 2N, and 3). Treatment is based on desmopressin, responsible for an increase in plasma concentration of von Willebrand factor, and plasma-derived von Willebrand factor concentrates which can be combined with factor VIII.